1630 
Arithmetic Subarrays 
Solution 

Medium 
Sort 
1629 
Slowest Key 
Solution 

Easy 
Array 
1626 
Best Team With No Conflicts 
Solution 

Medium 
DP 
1625 
Lexicographically Smallest String After Applying Operations 
Solution 

Medium 
BFS, DFS 
1624 
Largest Substring Between Two Equal Characters 
Solution 

Easy 
String 
1620 
Coordinate With Maximum Network Quality 
Solution 

Medium 
Greedy 
1619 
Mean of Array After Removing Some Elements 
Solution 

Easy 
Array 
1614 
Maximum Nesting Depth of the Parentheses 
Solution 

Easy 
String 
1609 
Even Odd Tree 
Solution 

Medium 
Tree 
1608 
Special Array With X Elements Greater Than or Equal X 
Solution 

Easy 
Array 
1604 
Alert Using Same KeyCard Three or More Times in a One Hour Period 
Solution 

Medium 
String, Ordered Map 
1603 
Design Parking System 
Solution 

Easy 
Design 
1601 
Maximum Number of Achievable Transfer Requests 
Solution 

Hard 
Backtracking 
1598 
Crawler Log Folder 
Solution 

Easy 
Stack 
1592 
Rearrange Spaces Between Words 
Solution 

Easy 
String 
1588 
Sum of All Odd Length Subarrays 
Solution 

Easy 
Array 
1583 
Count Unhappy Friends 
Solution 

Medium 
Array 
1582 
Special Positions in a Binary Matrix 
Solution 

Easy 
Array 
1576 
Replace All ?'s to Avoid Consecutive Repeating Characters 
Solution 
ğŸ“º 
Easy 
String 
1574 
Shortest Subarray to be Removed to Make Array Sorted 
Solution 

Medium 
Array, Binary Search 
1572 
Matrix Diagonal Sum 
Solution 

Easy 
Array 
1567 
Maximum Length of Subarray With Positive Product 
Solution 
ğŸ“º 
Medium 
Greedy 
1566 
Detect Pattern of Length M Repeated K or More Times 
Solution 
ğŸ“º 
Easy 
Array 
1561 
Maximum Number of Coins You Can Get 
Solution 
ğŸ“º 
Medium 
Sort 
1560 
Most Visited Sector in a Circular Track 
Solution 

Easy 
Array 
1558 
Minimum Numbers of Function Calls to Make Target Array 
Solution 

Medium 
Greedy 
1557 
Minimum Number of Vertices to Reach All Nodes 
Solution 

Medium 
Graph 
1556 
Thousand Separator 
Solution 
ğŸ“º 
Easy 
String 
1551 
Minimum Operations to Make Array Equal 
Solution 
ğŸ“º 
Medium 
Math 
1550 
Three Consecutive Odds 
Solution 

Easy 
Array 
1545 
Find Kth Bit in Nth Binary String 
Solution 
ğŸ“º 
Medium 
String 
1544 
Make The String Great 
Solution 
ğŸ“º 
Easy 
String, Stack 
1541 
Minimum Insertions to Balance a Parentheses String 
Solution 
ğŸ“º 
Medium 
String, Stack 
1539 
Kth Missing Positive Number 
Solution 
ğŸ“º 
Easy 
Array, HashTable 
1535 
Find the Winner of an Array Game 
Solution 
ğŸ“º 
Medium 
Array 
1534 
Count Good Triplets 
Solution 

Easy 
Array 
1528 
Shuffle String 
Solution 

Easy 
Sort 
1526 
Minimum Number of Increments on Subarrays to Form a Target Array 
Solution 

Hard 
Segment Tree 
1525 
Number of Good Ways to Split a String 
Solution 
ğŸ“º 
Medium 
String, Bit Manipulation 
1524 
Number of Subarrays With Odd Sum 
Solution 

Medium 
Array, Math 
1523 
Count Odd Numbers in an Interval Range 
Solution 
ğŸ“º 
Easy 
Math 
1518 
Water Bottles 
Solution 

Easy 
Greedy 
1514 
Path with Maximum Probability 
Solution 

Medium 
Graph 
1512 
Number of Good Pairs 
Solution 

Easy 
Array, HashTable, Math 
1508 
Range Sum of Sorted Subarray Sums 
Solution 

Medium 
Array, Sort 
1507 
Reformat Date 
Solution 

Easy 
String 
1502 
Can Make Arithmetic Progression From Sequence 
Solution 

Easy 
Array, Sort 
1496 
Path Crossing 
Solution 

Easy 
String 
1493 
Longest Subarray of 1's After Deleting One Element 
Solution 

Medium 
Array 
1492 
The kth Factor of n 
Solution 

Medium 
Math 
1491 
Average Salary Excluding the Minimum and Maximum Salary 
Solution 

Easy 
Array, Sort 
1487 
Making File Names Unique 
Solution 

Medium 
HashTable, String 
1486 
XOR Operation in an Array 
Solution 

Medium 
Array, Bit Manipulation 
1481 
Least Number of Unique Integers after K Removals 
Solution 

Medium 
Array, Sort 
1480 
Running Sum of 1d Array 
Solution, C++


Easy 
Array 
1476 
Subrectangle Queries 
Solution 

Medium 
Array 
1475 
Final Prices With a Special Discount in a Shop 
Solution 

Easy 
Array 
1471 
The k Strongest Values in an Array 
Solution 

Medium 
Array, Sort 
1470 
Shuffle the Array 
Solution, C++


Easy 
Array 
1469 
Find All The Lonely Nodes 
Solution 

Easy 
Tree, DFS 
1466 
Reorder Routes to Make All Paths Lead to the City Zero 
Solution 

Medium 
Tree, DFS 
1464 
Maximum Product of Two Elements in an Array 
Solution 

Easy 
Array 
1460 
Make Two Arrays Equal by Reversing Subarrays 
Solution 

Easy 
Array 
1457 
PseudoPalindromic Paths in a Binary Tree 
Solution 

Medium 
Bit Manipulation, Tree, DFS 
1456 
Maximum Number of Vowels in a Substring of Given Length 
Solution 

Medium 
String, Sliding Window 
1455 
Check If a Word Occurs As a Prefix of Any Word in a Sentence 
Solution 

Easy 
String 
1452 
People Whose List of Favorite Companies Is Not a Subset of Another List 
Solution 

Medium 
String, Sort 
1451 
Rearrange Words in a Sentence 
Solution 

Medium 
String, Sort 
1450 
Number of Students Doing Homework at a Given Time 
Solution 

Easy 
Array 
1448 
Count Good Nodes in Binary Tree 
Solution 

Medium 
Tree, DFS 
1447 
Simplified Fractions 
Solution 

Medium 
Math 
1446 
Consecutive Characters 
Solution 

Easy 
String 
1441 
Build an Array With Stack Operations 
Solution 

Easy 
Stack 
1437 
Check If All 1's Are at Least Length K Places Away 
Solution 

Medium 
Array 
1436 
Destination City 
Solution 

Easy 
String 
1432 
Max Difference You Can Get From Changing an Integer 
Solution 

Medium 
String 
1431 
Kids With the Greatest Number of Candies 
Solution, C++


Easy 
Array 
1428 
Leftmost Column with at Least a One 
Solution 

Medium 
Array 
1427 
Perform String Shifts 
Solution 

Easy 
Array, Math 
1426 
Counting Elements 
Solution 

Easy 
Array 
1423 
Maximum Points You Can Obtain from Cards 
Solution 

Medium 
Array, DP, Sliding Window 
1422 
Maximum Score After Splitting a String 
Solution 

Easy 
String 
1418 
Display Table of Food Orders in a Restaurant 
Solution 

Medium 
HashTable 
1417 
Reformat The String 
Solution 

Easy 
String 
1415 
The kth Lexicographical String of All Happy Strings of Length n 
Solution 

Medium 
Backtracking 
1413 
Minimum Value to Get Positive Step by Step Sum 
Solution 

Easy 
Array 
1410 
HTML Entity Parser 
Solution 

Medium 
String, Stack 
1409 
Queries on a Permutation With Key 
Solution 

Medium 
Array 
1408 
String Matching in an Array 
Solution 

Easy 
String 
1403 
Minimum Subsequence in NonIncreasing Order 
Solution 

Easy 
Greedy, Sort 
1402 
Reducing Dishes 
Solution 

Hard 
Dynamic Programming 
1401 
Circle and Rectangle Overlapping 
Solution 

Medium 
Geometry 
1400 
Construct K Palindrome Strings 
Solution 

Medium 
Greedy 
1399 
Count Largest Group 
Solution 

Easy 
Array 
1396 
Design Underground System 
Solution 

Medium 
Design 
1395 
Count Number of Teams 
Solution 

Medium 
Array 
1394 
Find Lucky Integer in an Array 
Solution 

Easy 
Array 
1392 
Longest Happy Prefix 
Solution 

Hard 
String, Rolling Hash 
1390 
Four Divisors 
Solution 

Medium 
Math 
1389 
Create Target Array in the Given Order 
Solution 

Easy 
Array 
1388 
Pizza With 3n Slices 
Solution 

Hard 
DP 
1387 
Sort Integers by The Power Value 
Solution 

Medium 
Sort, Graph 
1386 
Cinema Seat Allocation 
Solution 

Medium 
Array, Greedy 
1385 
Find the Distance Value Between Two Arrays 
Solution 

Easy 
Array 
1382 
Balance a Binary Search Tree 
Solution 

Medium 
Binary Search Tree 
1381 
Design a Stack With Increment Operation 
Solution 

Medium 
Stack, Design 
1380 
Lucky Numbers in a Matrix 
Solution 

Easy 
Array 
1379 
Find a Corresponding Node of a Binary Tree in a Clone of That Tree 
Solution 

Medium 
Tree 
1377 
Frog Position After T Seconds 
Solution 

Hard 
DFS, BFS 
1376 
Time Needed to Inform All Employees 
Solution 

Medium 
DFS 
1375 
Bulb Switcher III 
Solution 

Medium 
Array 
1374 
Generate a String With Characters That Have Odd Counts 
Solution 

Easy 
String 
1373 
Maximum Sum BST in Binary Tree 
Solution 

Hard 
DP, BST 
1372 
Longest ZigZag Path in a Binary Tree 
Solution 

Hard 
DP, Tree 
1371 
Find the Longest Substring Containing Vowels in Even Counts 
Solution 

Medium 
String 
1370 
Increasing Decreasing String 
Solution 

Easy 
String, Sort 
1367 
Linked List in Binary Tree 
Solution 

Medium 
DP, Linked List, Tree 
1366 
Rank Teams by Votes 
Solution 

Medium 
Array, Sort 
1365 
How Many Numbers Are Smaller Than the Current Number 
Solution 

Easy 
Array, HashTable 
1362 
Closest Divisors 
Solution 

Medium 
Math 
1361 
Validate Binary Tree Nodes 
Solution 

Medium 
Graph 
1360 
Number of Days Between Two Dates 
Solution 

Easy 

1358 
Number of Substrings Containing All Three Characters 
Solution 

Medium 
String 
1357 
Apply Discount Every n Orders 
Solution 

Medium 
Design 
1356 
Sort Integers by The Number of 1 Bits 
Solution 

Easy 
Sort, Bit Manipulation 
1354 
Construct Target Array With Multiple Sums 
Solution 

Hard 
Greedy 
1353 
Maximum Number of Events That Can Be Attended 
Solution 

Medium 
Greedy, Sort, Segment Tree 
1352 
Product of the Last K Numbers 
Solution 

Medium 
Array, Design 
1351 
Count Negative Numbers in a Sorted Matrix 
Solution 

Easy 
Array, Binary Search 
1349 
Maximum Students Taking Exam 
Solution 

Hard 
Dynamic Programming 
1348 
Tweet Counts Per Frequency 
Solution 

Medium 
Design 
1347 
Minimum Number of Steps to Make Two Strings Anagram 
Solution 

Easy 
String 
1346 
Check If N and Its Double Exist 
Solution 

Easy 
Array 
1345 
Jump Game IV 
Solution 

Hard 
BFS 
1344 
Angle Between Hands of a Clock 
Solution 

Medium 
Math 
1343 
Number of Subarrays of Size K and Average Greater than or Equal to Threshold 
Solution 

Medium 
Array 
1342 
Number of Steps to Reduce a Number to Zero 
Solution 

Easy 
Bit Manipulation 
1341 
The K Weakest Rows in a Matrix 
Solution 

Easy 

1339 
Maximum Product of Splitted Binary Tree 
Solution 

Medium 
DP, Tree 
1338 
Reduce Array Size to The Half 
Solution 

Medium 

1337 
Remove Palindromic Subsequences 
Solution 

Easy 
String 
1333 
Filter Restaurants by VeganFriendly, Price and Distance 
Solution 

Medium 

1331 
Rank Transform of an Array 
Solution 

Easy 

1329 
Sort the Matrix Diagonally 
Solution 

Medium 

1325 
Delete Leaves With a Given Value 
Solution 

Medium 
Tree 
1324 
Print Words Vertically 
Solution 

Medium 
String 
1323 
Maximum 69 Number 
Solution 

Easy 
Math 
1317 
Convert Integer to the Sum of Two NoZero Integers 
Solution 

Easy 

1315 
Sum of Nodes with EvenValued Grandparent 
Solution 

Medium 
Tree, DFS 
1314 
Matrix Block Sum 
Solution 

Medium 
Dynamic Programming 
1313 
Decompress RunLength Encoded List 
Solution 

Easy 
Array 
1305 
All Elements in Two Binary Search Trees 
Solution 

Medium 

1304 
Find N Unique Integers Sum up to Zero 
Solution 

Easy 

1302 
Deepest Leaves Sum 
Solution 

Medium 

1300 
Sum of Mutated Array Closest to Target 
Solution 

Medium 

1299 
Replace Elements with Greatest Element on Right Side 
Solution 

Easy 

1297 
Maximum Number of Occurrences of a Substring 
Solution 

Medium 

1296 
Divide Array in Sets of K Consecutive Numbers 
Solution 

Medium 

1295 
Find Numbers with Even Number of Digits 
Java Javascript

ğŸ“º 
Easy 

1291 
Sequential Digits 
Solution 

Medium 

1290 
Convert Binary Number in a Linked List to Integer 
Solution 

Easy 

1289 
Minimum Falling Path Sum II 
Solution 

Hard 
Dynamic Programming 
1287 
Element Appearing More Than 25% In Sorted Array 
Solution 
ğŸ“º 
Easy 

1286 
Iterator for Combination 
Solution 

Medium 
Backtracking, Design 
1282 
Group the People Given the Group Size They Belong To 
Solution 
ğŸ“º 
Medium 

1281 
Subtract the Product and Sum of Digits of an Integer 
Solution 

Easy 

1277 
Count Square Submatrices with All Ones 
Solution 

Medium 

1275 
Find Winner on a Tic Tac Toe Game 
Solution 

Easy 
Array 
1273 
Delete Tree Nodes 
Solution 

Medium 
Dynamic Programming, DFS 
1271 
Hexspeak 
Solution 

Easy 

1267 
Count Servers that Communicate 
Solution 

Medium 

1266 
Minimum Time Visiting All Points 
Solution 

Easy 

1265 
Print Immutable Linked List in Reverse 
Solution 

Medium 

1261 
Find Elements in a Contaminated Binary Tree 
Solution 

Medium 
Tree, HashTable 
1260 
Shift 2D Grid 
Solution 
ğŸ“º 
Easy 

1258 
Synonymous Sentences 
Solution 

Medium 
Backtracking 
1252 
Cells with Odd Values in a Matrix 
Solution 

Easy 

1237 
Find Positive Integer Solution for a Given Equation 
Solution 

Easy 

1243 
Array Transformation 
Solution 
ğŸ“º 
Easy 

1232 
Check If It Is a Straight Line 
Solution 
ğŸ“º 
Easy 

1228 
Missing Number In Arithmetic Progression 
Solution 

Easy 

1221 
Split a String in Balanced Strings 
Solution 

Easy 
Greedy 
1219 
Path with Maximum Gold 
Solution 

Medium 
Backtracking 
1217 
Play with Chips 
Solution 

Easy 
Array, Math, Greedy 
1214 
Two Sum BSTs 
Solution 

Medium 
Binary Search Tree 
1213 
Intersection of Three Sorted Arrays 
Solution 
ğŸ“º 
Easy 

1209 
Remove All Adjacent Duplicates in String II 
Solution 

Medium 
Stack 
1207 
Unique Number of Occurrences 
Solution 
ğŸ“º 
Easy 

1200 
Minimum Absolute Difference 
Solution 
ğŸ“º 
Easy 

1198 
Find Smallest Common Element in All Rows 
Solution 
ğŸ“º 
Easy 

1196 
How Many Apples Can You Put into the Basket 
Solution 
ğŸ“º 
Easy 

1190 
Reverse Substrings Between Each Pair of Parentheses 
Solution 

Medium 
Stack 
1189 
Maximum Number of Balloons 
Solution 
ğŸ“º 
Easy 

1185 
Day of the Week 
Solution 

Easy 

1184 
Distance Between Bus Stops 
Solution 
ğŸ“º 
Easy 

1182 
Shortest Distance to Target Color 
Solution 

Medium 
Binary Search 
1180 
Count Substrings with Only One Distinct Letter 
Solution 

Easy 
Math, String 
1176 
Diet Plan Performance 
Solution 

Easy 
Array, Sliding Window 
1175 
Prime Arrangements 
Solution 

Easy 

1165 
SingleRow Keyboard 
Solution 

Easy 

1161 
Maximum Level Sum of a Binary Tree 
Solution 

Medium 
Graph 
1160 
Find Words That Can Be Formed by Characters 
Solution 

Easy 

1154 
Day of the Year 
Solution 

Easy 

1150 
Check If a Number Is Majority Element in a Sorted Array 
Solution 
ğŸ“º 
Easy 

1137 
Nth Tribonacci Number 
Solution 

Easy 

1134 
Armstrong Number 
Solution 
ğŸ“º 
Easy 

1133 
Largest Unique Number 
Solution 
ğŸ“º 
Easy 

1128 
Number of Equivalent Domino Pairs 
Solution 
ğŸ“º 
Easy 

1122 
Relative Sort Array 
Solution 

Easy 

1170 
Compare Strings by Frequency of the Smallest Character 
Solution 

Easy 

1119 
Remove Vowels from a String 
Solution 
ğŸ“º 
Easy 

1118 
Number of Days in a Month 
Solution 

Easy 

1114 
Print in Order 
Solution 

Easy 

1108 
Defanging an IP Address 
Solution 
ğŸ“º 
Easy 

1104 
Path In Zigzag Labelled Binary Tree 
Solution 

Medium 
Math, Tree 
1103 
Distribute Candies to People 
Solution 

Easy 
Math 
1100 
Find KLength Substrings With No Repeated Characters 
Solution 

Medium 
String, Sliding Window 
1099 
Two Sum Less Than K 
Solution 
ğŸ“º 
Easy 

1089 
Duplicate Zeros 
Solution 

Easy 

1087 
Brace Expansion 
Solution 

Medium 
Backtracking 
1086 
High Five 
Solution 
ğŸ“º 
Easy 

1085 
Sum of Digits in the Minimum Number 
Solution 
ğŸ“º 
Easy 

1079 
Letter Tile Possibilities 
Solution 

Medium 

1078 
Occurrences After Bigram 
Solution 

Easy 

1071 
Greatest Common Divisor of Strings 
Solution 

Easy 

1066 
Campus Bikes II 
Solution 

Medium 
Backtracking, DP 
1065 
Index Pairs of a String 
Solution 

Medium 

1062 
Longest Repeating Substring 
Solution 

Medium 

1057 
Campus Bikes 
Solution 

Medium 

1056 
Confusing Number 
Solution 

Easy 

1055 
Fixed Point 
Solution 

Easy 

1051 
Height Checker 
Solution 

Easy 

1047 
Remove All Adjacent Duplicates In String 
Solution 

Easy 

1046 
Last Stone Weight 
Solution 
ğŸ“º 
Easy 

1043 
Partition Array for Maximum Sum 
Solution 

Medium 
DP 
1038 
Binary Search Tree to Greater Sum Tree 
Solution 

Medium 
DFS, tree 
1037 
Valid Boomerang 
Solution 

Easy 
Math 
1033 
Moving Stones Until Consecutive 
Solution 

Easy 
Math 
1030 
Matrix Cells in Distance Order 
Solution 

Easy 

1029 
Two City Scheduling 
Solution 

Easy 

1025 
Divisor Game 
Solution 

Easy 

1022 
Sum of Root To Leaf Binary Numbers 
Solution 

Easy 

1021 
Remove Outermost Parentheses 
Solution 

Easy 

1020 
Number of Enclaves 
Solution 

Medium 
Graph, DFS, BFS, recursion 
1019 
Next Greater Node In Linked List 
Solution 

Medium 
Linked List, Stack 
1018 
Binary Prefix Divisible By 5 
Solution 

Easy 

1014 
Best Sightseeing Pair 
Solution 

Medium 

1013 
Partition Array Into Three Parts With Equal Sum 
Solution 

Easy 

1011 
Capacity To Ship Packages Within D Days 
Solution 

Medium 
Binary Search 
1010 
Pairs of Songs With Total Durations Divisible by 60 
Solution 

Easy 

1009 
Complement of Base 10 Integer 
Solution 

Easy 

1008 
Construct Binary Search Tree from Preorder Traversal 
Solution 

Medium 
Recursion 
1005 
Maximize Sum Of Array After K Negations 
Solution 
ğŸ“º 
Easy 

1004 
Max Consecutive Ones III 
Solution 

Medium 
Two Pointers, Sliding Window 
1003 
Check If Word Is Valid After Substitutions 
Solution 

Medium 

1002 
Find Common Characters 
Solution 

Easy 

999 
Available Captures for Rook 
Solution 

Easy 

997 
Find the Town Judge 
Solution 

Easy 

994 
Rotting Oranges 
Solution 

Easy 
BFS 
993 
Cousins in Binary Tree 
Solution 

Easy 
Tree, BFS 
989 
Add to ArrayForm of Integer 
Solution 

Easy 
Array 
988 
Smallest String Starting From Leaf 
Solution 

Medium 
Tree, DFS 
987 
Vertical Order Traversal of a Binary Tree 
Solution 

Medium 
Recursion 
986 
Interval List Intersections 
Solution 

Medium 
Two Pointers 
985 
Sum of Even Numbers After Queries 
Solution 

Easy 
Array 
980 
Unique Paths III 
Solution 

Hard 
Backtracking, DFS 
979 
Distribute Coins in Binary Tree 
Solution 

Medium 
Recursion 
977 
Squares of a Sorted Array 
Solution 

Easy 
Array 
976 
Largest Perimeter Triangle 
Solution 

Easy 
Math Array 
974 
Subarray Sums Divisible by K 
Solution 

Medium 
Array 
973 
K Closest Points to Origin 
Solution 

Easy 
Math Sort 
970 
Powerful Integers 
Solution 

Easy 
Math 
966 
Vowel Spellchecker 
Solution 

Medium 
Hash Table, String 
965 
Univalued Binary Tree 
Solution 

Easy 
DFS, recursion 
961 
NRepeated Element in Size 2N Array 
Solution 

Easy 

958 
Check Completeness of a Binary Tree 
Solution 

Medium 
Tree 
957 
Prison Cells After N Days 
Solution 

Medium 

954 
Array of Doubled Pairs 
Solution 
ğŸ“º 
Medium 

953 
Verifying an Alien Dictionary 
Solution 

Easy 

951 
Flip Equivalent Binary Trees 
Solution 

Medium 
Tree, DFS, recursion 
950 
Reveal Cards In Increasing Order 
Solution 

Medium 

946 
Validate Stack Sequences 
Solution 

Medium 
Stack 
944 
Delete Columns to Make Sorted 
Solution 

Easy 

942 
DI String Match 
Solution 

Easy 

941 
Valid Mountain Array 
Solution 

Easy 

938 
Range Sum of BST 
Solution 

Medium 
BST, recursion, DFS 
937 
Reorder Log Files 
Solution 

Easy 

935 
Knight Dialer 
Solution 

Medium 

933 
Number of Recent Calls 
Solution 

Easy 

931 
Minimum Falling Path Sum 
Solution 

Medium 
Dynamic Programming 
929 
Unique Email Addresses 
Solution 

Easy 

925 
Long Pressed Name 
Solution 

Easy 

922 
Sort Array By Parity II 
Solution 

Easy 

921 
Minimum Add to Make Parentheses Valid 
Solution 

Medium 
Stack, Greedy 
917 
Reverse Only Letters 
Solution 

Easy 

914 
X of a Kind in a Deck of Cards 
Solution 

Easy 

912 
Sort an Array 
Solution 

Easy 

908 
Smallest Range I 
Solution 

Easy 

901 
Online Stock Span 
Solution 

Medium 
Stack 
900 
RLE Iterator 
Solution 

Medium 

897 
Increasing Order Search Tree 
Solution 

Easy 
DFS, recursion 
896 
Monotonic Array 
Solution 

Easy 

890 
Find and Replace Pattern 
Solution 

Medium 

893 
Groups of SpecialEquivalent Strings 
Solution 
ğŸ“º 
Easy 

888 
Fair Candy Swap 
Solution 

Easy 

885 
Spiral Matrix III 
Solution 
ğŸ“º 
Medium 

884 
Uncommon Words from Two Sentences 
Solution 

Easy 

883 
Projection Area of 3D Shapes 
Solution 

Easy 
Math 
880 
Decoded String at Index 
Solution 

Medium 
Stack 
876 
Middle of the Linked List 
Solution 

Easy 

872 
LeafSimilar Trees 
Solution 

Easy 
DFS, recursion 
868 
Binary Gap 
Solution 

Easy 

867 
Transpose Matrix 
Solution 

Easy 

860 
Lemonade Change 
Solution 

Easy 

859 
Buddy Strings 
Solution 

Easy 

856 
Score of Parentheses 
Solution 

Medium 
Stack, String 
852 
Peak Index in a Mountain Array 
Solution 

Easy 

849 
Maximize Distance to Closest Person 
Solution 

Easy 

844 
Backspace String Compare 
Solution 

Easy 

841 
Keys and Rooms 
Solution 

Easy 
DFS, Graph 
840 
Magic Squares In Grid 
Solution 

Easy 

836 
Rectangle Overlap 
Solution 
ğŸ“º 
Easy 

832 
Flipping an Image 
Solution 

Easy 

830 
Positions of Large Groups 
Solution 

Easy 

824 
Goat Latin 
Solution 

Easy 

821 
Shortest Distance to a Character 
Solution 

Easy 

819 
Most Common Word 
Solution 

Easy 
HashMap 
814 
Binary Tree Pruning 
Solution 

Medium 
recursion, DFS 
811 
Subdomain Visit Count 
Solution 

Easy 
HashMap 
807 
Max Increase to Keep City Skyline 
Solution 

Medium 

806 
Number of Lines To Write String 
Solution 

Easy 

804 
Unique Morse Code Words 
Solution 

Easy 

800 
Similar RGB Color 
Solution 

Easy 

799 
Champagne Tower 
Solution 

Medium 

796 
Rotate String 
Solution 

Easy 

791 
Custom Sort String 
Solution 

Medium 

789 
Escape The Ghosts 
Solution 

Medium 
Math 
788 
Rotated Digits 
Solution 

Easy 

784 
Letter Case Permutation 
Solution 

Easy 

783 
Minimum Distance Between BST Nodes 
Solution 

Easy 

779 
Kth Symbol in Grammar 
Solution 

Medium 

776 
Split BST 
Solution 

Medium 
Recursion 
771 
Jewels and Stones 
Solution 

Easy 

769 
Max Chunks To Make Sorted 
Solution 

Medium 
Array 
767 
Reorganize String 
Solution 

Medium 

766 
Toeplitz Matrix 
Solution 

Easy 

765 
Couples Holding Hands 
Solution 

Hard 

764 
Largest Plus Sign 
Solution 

Medium 
DP 
763 
Partition Labels 
Solution 

Medium 

762 
Prime Number of Set Bits in Binary Representation 
Solution 

Easy 

760 
Find Anagram Mappings 
Solution 

Easy 

758 
Bold Words in String 
Solution 

Easy 

756 
Pyramid Transition Matrix 
Solution 

Medium 
Backtracking 
755 
Pour Water 
Solution 

Medium 
Array 
754 
Reach a Number 
Solution 

Medium 
Math 
750 
Number Of Corner Rectangles 
Solution 

Medium 

748 
Shortest Completing Word 
Solution 

Easy 

747 
Largest Number Greater Than Twice of Others 
Solution 

Easy 

746 
Min Cost Climbing Stairs 
Solution 

Easy 

744 
Find Smallest Letter Greater Than Target 
Solution 

Easy 

743 
Network Delay Time 
Solution 

Medium 
Graph, Djikstra 
742 
Closest Leaf in a Binary Tree 
Solution 

Medium 
Tree 
740 
Delete and Earn 
Solution 

Medium 

739 
Daily Temperatures 
Solution 

Medium 

738 
Monotone Increasing Digits 
Solution 

Medium 

737 
Sentence Similarity II 
Solution 

Medium 
Union Find 
735 
Asteroid Collision 
Solution 

Medium 
Stack 
734 
Sentence Similarity 
Solution 

Easy 
HashTable 
733 
Flood Fill 
Solution 

Easy 
BFS, DFS 
729 
My Calendar I 
Solution 

Medium 

728 
Self Dividing Numbers 
Solution 

Easy 

727 
Minimum Window Subsequence 
Solution 

Hard 
DP 
725 
Split Linked List in Parts 
Solution 

Medium 
LinkedList 
724 
Find Pivot Index 
Solution 

Easy 
Array 
723 
Candy Crush 
Solution 

Medium 
Array, Two Pointers 
721 
Accounts Merge 
Solution 

Medium 
DFS, Union Find 
720 
Longest Word in Dictionary 
Solution 

Easy 
Trie 
719 
Find Kth Smallest Pair Distance 
Solution 

Hard 
Binary Search 
718 
Maximum Length of Repeated Subarray 
Solution 

Medium 
DP 
717 
1bit and 2bit Characters 
Solution 

Easy 

716 
Max Stack 
Solution 

Hard 
Design 
714 
Best Time to Buy and Sell Stock with Transaction Fee 
Solution 

Medium 
DP 
713 
Subarray Product Less Than K 
Solution 

Medium 

712 
Minimum ASCII Delete Sum for Two Strings 
Solution 

Medium 
DP 
709 
To Lower Case 
Solution 

Easy 
String 
706 
Design HashMap 
Solution 

Easy 
Design 
705 
Design HashSet 
Solution 

Easy 
Design 
704 
Binary Search 
Solution 

Easy 
Binary Search 
703 
Kth Largest Element in a Stream 
Solution 

Easy 

701 
Insert into a Binary Search Tree 
Solution 

Medium 
DFS, recursion 
700 
Search in a Binary Search Tree 
Solution 

Easy 
recusion, dfs 
699 
Falling Squares 
Solution 

Hard 
Segment Tree 
698 
Partition to K Equal Sum Subsets 
Solution, C++


Medium 
Backtracking + DP 
697 
Degree of an Array 
Solution 

Easy 

696 
Count Binary Substrings 
Solution 

Easy 

695 
Max Area of Island 
Solution 

Easy 
DFS 
694 
Number of Distinct Islands 
Solution 

Medium 
DFS 
693 
Binary Number with Alternating Bits 
Solution 

Easy 

692 
Top K Frequent Words 
Solution 

Medium 

691 
Stickers to Spell Word 
Solution 

Hard 
DP 
690 
Employee Importance 
Solution 

Easy 
DFS 
689 
Maximum Sum of 3 NonOverlapping Subarrays 
Solution 

Hard 
DP 
688 
Knight Probability in Chessboard 
Solution 

Medium 
DP 
687 
Longest Univalue Path 
Solution 

Easy 
DFS 
686 
Repeated String Match 
Solution 

Easy 

685 
Redundant Connection II 
Solution 

Hard 
Union Find 
684 
Redundant Connection 
Solution 

Medium 
Union Find 
683 
K Empty Slots 
Solution 

Hard 

682 
Baseball Game 
Solution 

Easy 

681 
Next Closest Time 
Solution 

Medium 

680 
Valid Palindrome II 
Solution 

Easy 
String 
679 
24 Game 
Solution 

Hard 
Recursion 
678 
Valid Parenthesis String 
Solution 

Medium 
Recursion, Greedy 
677 
Map Sum Pairs 
Solution 

Medium 
HashMap, Trie 
676 
Implement Magic Dictionary 
Solution 

Medium 

675 
Cut Off Trees for Golf Event 
Solution 

Hard 
BFS 
674 
Longest Continuous Increasing Subsequence 
Solution 

Easy 

673 
Number of Longest Increasing Subsequence 
Solution 

Medium 
DP 
672 
Bulb Switcher II 
Solution 

Medium 
Math 
671 
Second Minimum Node In a Binary Tree 
Solution 

Easy 
Tree, DFS 
670 
Maximum Swap 
Solution 

Medium 
String 
669 
Trim a Binary Search Tree 
Solution 

Easy 
Tree, DFS 
668 
Kth Smallest Number in Multiplication Table 
Solution 

Hard 
Binary Search 
667 
Beautiful Arrangement II 
Solution 

Medium 
Array 
666 
Path Sum IV 
Solution 

Medium 
Tree, DFS 
665 
Nondecreasing Array 
Solution 

Easy 

664 
Strange Printer 
Solution 

Hard 
DP 
663 
Equal Tree Partition 
Solution 

Medium 
Tree 
662 
Maximum Width of Binary Tree 
Solution 

Medium 
BFS, DFS 
661 
Image Smoother 
Solution 

Easy 
Array 
660 
Remove 9 
Solution 

Hard 
Math 
659 
Split Array into Consecutive Subsequences 
Solution 

Medium 
HashMap 
658 
Find K Closest Elements 
Solution 

Medium 

657 
Judge Route Circle 
Solution 

Easy 

656 
Coin Path 
Solution 

Hard 
DP 
655 
Print Binary Tree 
Solution 

Medium 
Recursion 
654 
Maximum Binary Tree 
Solution 

Medium 
Tree 
653 
Two Sum IV  Input is a BST 
Solution 

Easy 
Tree 
652 
Find Duplicate Subtrees 
Solution 

Medium 
Tree 
651 
4 Keys Keyboard 
Solution 

Medium 
DP 
650 
2 Keys Keyboard 
Solution 

Medium 
DP 
649 
Dota2 Senate 
Solution 

Medium 
Greedy 
648 
Replace Words 
Solution 

Medium 
Trie 
647 
Palindromic Substrings 
Solution 

Medium 
DP 
646 
Maximum Length of Pair Chain 
Solution 

Medium 
DP, Greedy 
645 
Set Mismatch 
Solution 

Easy 

644 
Maximum Average Subarray II 
Solution 

Hard 
Binary Search 
643 
Maximum Average Subarray I 
Solution 

Easy 

642 
Design Search Autocomplete System 
Solution 

Hard 
Design 
640 
Solve the Equation 
Solution 

Medium 

639 
Decode Ways II 
Solution 

Hard 
DP 
638 
Shopping Offers 
Solution 

Medium 
DP, DFS 
637 
Average of Levels in Binary Tree 
Solution 

Easy 

636 
Exclusive Time of Functions 
Solution 

Medium 
Stack 
635 
Design Log Storage System 
Solution 

Medium 
Design 
634 
Find the Derangement of An Array 
Solution 

Medium 
Math 
633 
Sum of Square Numbers 
Solution 

Easy 
Binary Search 
632 
Smallest Range 
Solution 

Hard 
Heap 
631 
Design Excel Sum Formula 
Solution 

Hard 
Design, Topological Sort 
630 
Course Schedule III 
Solution 

Hard 
Heap, Greedy 
629 
K Inverse Pairs Array 
Solution 

Hard 
DP 
628 
Maximum Product of Three Numbers 
Solution 

Easy 

625 
Minimum Factorization 
Solution 

Medium 

624 
Maximum Distance in Arrays 
Solution 

Easy 
Sort, Array 
623 
Add One Row to Tree 
Solution 

Medium 
Tree 
621 
Task Scheduler 
Solution 

Medium 
Greedy, Queue 
617 
Merge Two Binary Trees 
Solution 

Easy 
Tree, Recursion 
616 
Add Bold Tag in String 
Solution 

Medium 
String 
611 
Valid Triangle Number 
Solution 

Medium 
Binary Search 
609 
Find Duplicate File in System 
Solution 

Medium 
HashMap 
606 
Construct String from Binary Tree 
Solution 

Easy 
Tree, Recursion 
605 
Can Place Flowers 
Solution 

Easy 
Array 
604 
Design Compressed String Iterator 
Solution 

Easy 
Design, String 
600 
Nonnegative Integers without Consecutive Ones 
Solution 

Hard 
Bit Manipulation, DP 
599 
Minimum Index Sum of Two Lists 
Solution 

Easy 
HashMap 
598 
Range Addition II 
Solution 

Easy 

594 
Longest Harmonious Subsequence 
Solution 

Easy 
Array, HashMap 
593 
Valid Square 
Solution 

Medium 
Math 
592 
Fraction Addition and Subtraction 
Solution 

Medium 
Math 
591 
Tag Validator 
Solution 

Hard 
Stack, String 
590 
Nary Tree Postorder Traversal 
Solution 

Easy 
DFS, recursion 
589 
Nary Tree Preorder Traversal 
Solution 

Easy 
DFS, recursion 
588 
Design InMemory File System 
Solution 

Hard 
Trie, Design 
587 
Erect the Fence 
Solution 

Hard 
Geometry 
583 
Delete Operation for Two Strings 
Solution 

Medium 
DP 
582 
Kill Process 
Solution 

Medium 
Stack 
581 
Shortest Unsorted Continuous Subarray 
Solution 

Easy 
Array, Sort 
576 
Out of Boundary Paths 
Solution 

Hard 
DP, DFS 
575 
Distribute Candies 
Solution 

Easy 
Array 
573 
Squirrel Simulation 
Solution 

Medium 
Math 
572 
Subtree of Another Tree 
Solution 

Easy 
Tree 
568 
Maximum Vacation Days 
Solution 

Hard 
DP 
567 
Permutation in String 
Solution 

Medium 
Sliding Windows, Two Pointers 
566 
Reshape the Matrix 
Solution 

Easy 

565 
Array Nesting 
Solution 

Medium 

563 
Binary Tree Tilt 
Solution 

Easy 
Tree Recursion 
562 
Longest Line of Consecutive One in Matrix 
Solution 

Medium 
Matrix DP 
561 
Array Partition I 
Solution 

Easy 
Array 
560 
Subarray Sum Equals K 
Solution 

Medium 
Array, HashMap 
559 
Maximum Depth of Nary Tree 
Solution 

Easy 
DFS, recursion 
557 
Reverse Words in a String III 
Solution 

Easy 
String 
556 
Next Greater Element III 
Solution 

Medium 
String 
555 
Split Concatenated Strings 
Solution 

Medium 
String 
554 
Brick Wall 
Solution 

Medium 
HashMap 
553 
Optimal Division 
Solution 

Medium 
String, Math 
552 
Student Attendance Record II 
Solution 

Hard 
DP 
551 
Student Attendance Record I 
Solution 

Easy 
String 
549 
Binary Tree Longest Consecutive Sequence II 
Solution 

Medium 
Tree 
548 
Split Array with Equal Sum 
Solution 

Medium 
Array 
547 
Friend Circles 
Solution 

Medium 
Union Find 
546 
Remove Boxes 
Solution 

Hard 
DFS, DP 
545 
Boundary of Binary Tree 
Solution 

Medium 
Recursion 
544 
Output Contest Matches 
Solution 

Medium 
Recursion 
543 
Diameter of Binary Tree 
Solution 

Easy 
Tree/DFS/Recursion 
542 
01 Matrix 
Solution 

Medium 
BFS 
541 
Reverse String II 
Solution 

Easy 
String 
540 
Single Element in a Sorted Array 
Solution 

Medium 

539 
Minimum Time Difference 
Solution 

Medium 
String 
538 
Convert BST to Greater Tree 
Solution 

Easy 
Tree 
537 
Complex Number Multiplication 
Solution 

Medium 
Math, String 
536 
Construct Binary Tree from String 
Solution 

Medium 
Recursion, Stack 
535 
Encode and Decode TinyURL 
Solution 

Medium 
Design 
533 
Lonely Pixel II 
Solution 

Medium 
HashMap 
532 
Kdiff Pairs in an Array 
Solution 

Easy 
HashMap 
531 
Lonely Pixel I 
Solution 

Medium 

530 
Minimum Absolute Difference in BST 
Solution 

Easy 
DFS 
529 
Minesweeper 
Solution 

Medium 
BFS 
527 
Word Abbreviation 
Solution 

Hard 

526 
Beautiful Arrangement 
Solution 

Medium 
Backtracking 
525 
Contiguous Array 
Solution 

Medium 
HashMap 
524 
Longest Word in Dictionary through Deleting 
Solution 

Medium 
Sort 
523 
Continuous Subarray Sum 
Solution 

Medium 
DP 
522 
Longest Uncommon Subsequence II 
Solution 

Medium 

521 
Longest Uncommon Subsequence I 
Solution 

Easy 

520 
Detect Capital 
Solution 

Easy 

517 
Super Washing Machines 
Solution 

Hard 
DP 
516 
Longest Palindromic Subsequence 
Solution 

Medium 
DP 
515 
Find Largest Value in Each Tree Row 
Solution 

Medium 
BFS 
514 
Freedom Trail 
Solution 

Hard 
DP 
513 
Find Bottom Left Tree Value 
Solution 

Medium 
BFS 
509 
Fibonacci Number 
Solution 
ğŸ“º 
Easy 
Array 
508 
Most Frequent Subtree Sum 
Solution 

Medium 
DFS, Tree 
507 
Perfect Number 
Solution 

Easy 
Math 
506 
Relative Ranks 
Solution 

Easy 

505 
The Maze II 
Solution 

Medium 
BFS 
504 
Base 7 
Solution 

Easy 

503 
Next Greater Element II 
Solution 

Medium 
Stack 
502 
IPO 
Solution 

Hard 
Heap, Greedy 
501 
Find Mode in Binary Tree 
Solution 

Easy 
Binary Tree 
500 
Keyboard Row 
Solution 

Easy 

499 
The Maze III 
Solution 

Hard 
BFS 
496 
Next Greater Element I 
Solution 

Easy 

498 
Diagonal Traverse 
Solution 

Medium 

495 
Teemo Attacking 
Solution 

Medium 
Array 
494 
Target Sum 
Solution 

Medium 

493 
Reverse Pairs 
Solution 

Hard 
Recursion 
492 
Construct the Rectangle 
Solution 

Easy 
Array 
491 
Increasing Subsequences 
Solution 

Medium 
Backtracking, DFS 
490 
The Maze 
Solution 

Medium 
BFS 
488 
Zuma Game 
Solution 

Hard 
DFS, Backtracking 
487 
Max Consecutive Ones II 
Solution 

Medium 
Array 
486 
Predict the Winner 
Solution 

Medium 
DP 
485 
Max Consecutive Ones 
Java Javascript


Easy 
Array 
484 
Find Permutation 
Solution 

Medium 
Array, String, Greedy 
483 
Smallest Good Base 
Solution 

Hard 
Binary Search, Math 
482 
License Key Formatting 
Solution 

Medium 

481 
Magical String 
Solution 

Medium 

480 
Sliding Window Median 
Solution 

Hard 
Heap 
479 
Largest Palindrome Product 
Solution 

Easy 

477 
Total Hamming Distance 
Solution 

Medium 
Bit Manipulation 
476 
Number Complement 
Solution 

Easy 
Bit Manipulation 
475 
Heaters 
Solution 

Easy 
Array Binary Search 
474 
Ones and Zeroes 
Solution 

Medium 
DP 
473 
Matchsticks to Square 
Solution 

Medium 
Backtracking, DFS 
472 
Concatenated Words 
Solution 

Hard 
Trie, DP, DFS 
471 
Encode String with Shortest Length 
Solution 

Hard 
DP 
469 
Convex Polygon 
Solution 

Medium 
Math 
468 
Validate IP Address 
Solution 

Medium 
String 
467 
Unique Substrings in Wraparound String 
Solution 

Medium 
DP 
466 
Count The Repetitions 
Solution 

Hard 
DP 
465 
Optimal Account Balancing 
Solution 

Hard 
DP 
464 
Can I Win 
Solution 

Medium 
DP 
463 
Island Perimeter 
Solution 

Easy 

462 
Minimum Moves to Equal Array Elements II 
Solution 

Medium 

461 
Hamming Distance 
Solution, C++


Easy 

460 
LFU Cache 
Solution 

Hard 
Design, LinkedHashMap, HashMap 
459 
Repeated Substring Pattern 
Solution 

Easy 
String, KMP 
458 
Poor Pigs 
Solution 

Easy 
Math 
457 
Circular Array Loop 
Solution 

Medium 

456 
132 Pattern 
Solution 

Medium 
Stack 
455 
Assign Cookies 
Solution 

Easy 

454 
4Sum II 
Solution 

Medium 
HashMap 
453 
Minimum Moves to Equal Array Elements 
Solution 

Easy 

452 
Minimum Number of Arrows to Burst Balloons 
Solution 

Medium 
Array, Greedy 
451 
Sort Characters By Frequency 
Solution 

Medium 
HashMap 
450 
Delete Node in a BST 
Solution 

Medium 
Tree, Recursion 
449 
Serialize and Deserialize BST 
Solution 

Medium 
BFS 
448 
Find All Numbers Disappeared in an Array 
Solution 

Easy 
Array, HashMap 
447 
Number of Boomerangs 
Solution 

Easy 
HashMap 
446 
Arithmetic Slices II  Subsequence 
Solution 

Hard 
DP 
445 
Add Two Numbers II 
Solution 

Medium 
Stack, LinkedList 
444 
Sequence Reconstruction 
Solution 

Medium 
Topological Sort, Graph 
443 
String Compression 
Solution 

Easy 

442 
Find All Duplicates in an Array 
Solution 

Medium 
Array 
441 
Arranging Coins 
Solution 

Easy 

440 
Kth Smallest in Lexicographical Order 
Solution 

Hard 

439 
Ternary Expression Parser 
Solution 

Medium 
Stack 
438 
Find All Anagrams in a String 
Solution 

Easy 
Sliding Window 
437 
Path Sum III 
Solution 

Easy 
DFS, recursion 
436 
Find Right Interval 
Solution 

Medium 
Binary Search 
435 
Nonoverlapping Intervals 
Solution 

Medium 
Greedy 
434 
Number of Segments in a String 
Solution 

Easy 

432 
All O`one Data Structure 
Solution 

Hard 
Design 
429 
Nary Tree Level Order Traversal 
Solution 

Easy 
BFS, Tree 
425 
Word Squares 
Solution 

Hard 
Trie, Backtracking, Recursion 
424 
Longest Repeating Character Replacement 
Solution 

Medium 
Sliding Window 
423 
Reconstruct Original Digits from English 
Solution 

Medium 
Math 
422 
Valid Word Square 
Solution 

Easy 

421 
Maximum XOR of Two Numbers in an Array 
Solution 

Medium 
Bit Manipulation, Trie 
420 
Strong Password Checker 
Solution 

Hard 

419 
Battleships in a Board 
Solution 

Medium 
DFS 
418 
Sentence Screen Fitting 
Solution 

Medium 

417 
Pacific Atlantic Water Flow 
Solution 

Medium 
DFS 
416 
Partition Equal Subset Sum 
Java, C++


Medium 
DP 
415 
Add Strings 
Solution 

Easy 

414 
Third Maximum Number 
Solution 

Easy 

413 
Arithmetic Slices 
Solution 

Medium 
DP 
412 
Fizz Buzz 
Solution 

Easy 

411 
Minimum Unique Word Abbreviation 
Solution 

Hard 
NPHard, Backtracking, Trie, Recursion 
410 
Split Array Largest Sum 
Solution 

Hard 
Binary Search, DP 
409 
Longest Palindrome 
Solution 

Easy 

408 
Valid Word Abbreviation 
Solution 

Easy 

407 
Trapping Rain Water II 
Solution 

Hard 
Heap 
406 
Queue Reconstruction by Height 
Solution 

Medium 
LinkedList, PriorityQueue 
405 
Convert a Number to Hexadecimal 
Solution 

Easy 

404 
Sum of Left Leaves 
Solution 

Easy 

403 
Frog Jump 
Solution 

Hard 
DP 
402 
Remove K Digits 
Solution 

Medium 
Greedy, Stack 
401 
Binary Watch 
Solution 

Easy 

400 
Nth Digit 
Solution 

Easy 

399 
Evaluate Division 
Solution 

Medium 
Graph, DFS, Backtracking 
398 
Random Pick Index 
Solution 

Medium 
Reservoir Sampling 
397 
Integer Replacement 
Solution 

Easy 
BFS 
396 
Rotate Function 
Solution 

Easy 

395 
Longest Substring with At Least K Repeating Characters 
Solution 

Medium 
Recursion 
394 
Decode String 
Solution 

Medium 
Stack Depthfirstsearch 
393 
UTF8 Validation 
Solution 

Medium 
Bit Manipulation 
392 
Is Subsequence 
Solution 

Medium 
Array, String 
391 
Perfect Rectangle 
Solution 

Hard 

390 
Elimination Game 
Solution 

Medium 

389 
Find the Difference 
Solution 


Easy 
388 
Longest Absolute File Path 
Solution 

Medium 
Stack 
387 
First Unique Character in a String 
Solution 

Easy 
HashMap 
386 
Lexicographical Numbers 
Solution 

Medium 

385 
Mini Parser 
Solution 

Medium 
Stack 
384 
Shuffle an Array 
Solution 

Medium 

383 
Ransom Note 
Solution 

Easy 
String 
382 
Linked List Random Node 
Solution 

Medium 
Reservoir Sampling 
381 
Insert Delete GetRandom O(1)  Duplicates allowed 
Solution 

Hard 

380 
Insert Delete GetRandom O(1) 
Solution 

Medium 
Design, HashMap 
379 
Design Phone Directory 
Solution 

Medium 

378 
Kth Smallest Element in a Sorted Matrix 
Solution 

Medium 
Binary Search 
377 
Combination Sum IV 
Solution 

Medium 
DP 
376 
Wiggle Subsequence 
Solution 

Medium 
DP, Greedy 
375 
Guess Number Higher or Lower II 
Solution 

Medium 
DP 
374 
Guess Number Higher or Lower 
Solution 

Easy 
Binary Search 
373 
Find K Pairs with Smallest Sums 
Solution 

Medium 
Heap 
372 
Super Pow 
Solution 

Medium 
Math 
371 
Sum of Two Integers 
Solution 

Easy 

370 
Range Addition 
Solution 

Medium 
Array 
369 
Plus One Linked List 
Solution 

Medium 
Linked List 
368 
Largest Divisible Subset 
Solution 

Medium 
DP 
367 
Valid Perfect Square 
Solution 

Medium 

366 
Find Leaves of Binary Tree 
Solution 

Medium 
DFS 
365 
Water and Jug Problem 
Solution 

Medium 
Math 
364 
Nested List Weight Sum II 
Solution 

Medium 
DFS 
363 
Max Sum of Rectangle No Larger Than K 
Solution 

Hard 
DP 
362 
Design Hit Counter 
Solution 

Medium 
Design 
361 
Bomb Enemy 
Solution 

Medium 

360 
Sort Transformed Array 
Solution 

Medium 
Two Pointers, Math 
359 
Logger Rate Limiter 
Solution 

Easy 
HashMap 
358 
Rearrange String k Distance Apart 
Solution 

Hard 
HashMap, Heap, Greedy 
357 
Count Numbers with Unique Digits 
Solution 

Medium 
DP, Math 
356 
Line Reflection 
Solution 

Medium 
HashSet 
355 
Design Twitter 
Solution 

Medium 
Design, HashMap, Heap 
354 
Russian Doll Envelopes 
Solution 

Hard 
DP, Binary Search 
353 
Design Snake Game 
Solution 

Medium 

352 
Data Stream as Disjoint Intervals 
Solution 

Hard 
TreeMap 
351 
Android Unlock Patterns 
Solution 

Medium 

350 
Intersection of Two Arrays II 
Solution 
ğŸ“º 
Easy 
HashMap, Binary Search 
349 
Intersection of Two Arrays 
Solution 
ğŸ“º 
Easy 
Two Pointers, Binary Search 
348 
Design TicTacToe 
Solution 

Medium 
Design 
347 
Top K Frequent Elements 
Solution 

Medium 
HashTable, Heap, Bucket Sort 
346 
Moving Average from Data Stream 
Solution 

Easy 
Queue 
345 
Reverse Vowels of a String 
Solution 

Easy 
String 
344 
Reverse String 
Solution 
ğŸ“º 
Easy 
String 
343 
Integer Break 
Solution 

Medium 
Math 
342 
Power of Four 
Solution 

Easy 
Math 
341 
Flatten Nested List Iterator 
Solution 

Medium 
Stack 
340 
Longest Substring with At Most K Distinct Characters 
Solution 

Hard 
Sliding Window 
339 
Nested List Weight Sum 
Solution 

Easy 
DFS 
338 
Counting Bits 
Solution 

Medium 

337 
House Robber III 
Solution 

Medium 
DP 
336 
Palindrome Pairs 
Solution 

Hard 

335 
Self Crossing 
Solution 

Hard 
Math 
334 
Increasing Triplet Subsequence 
Solution 

Medium 

333 
Largest BST Subtree 
Solution 

Medium 
Tree 
332 
Reconstruct Itinerary 
Solution 

Medium 
Graph, DFS 
331 
Verify Preorder Serialization of a Binary Tree 
Solution 

Medium 
Stack 
330 
Patching Array 
Solution 

Hard 
Greedy 
329 
Longest Increasing Path in a Matrix 
Solution 

Hard 
DFS, DP 
328 
Odd Even Linked List 
Solution 

Medium 
Linked List 
327 
Count of Range Sum 
Solution 

Hard 
BST, Divide and Conquer 
326 
Power of Three 
Solution 

Easy 
Math 
325 
Maximum Size Subarray Sum Equals k 
Solution 

Medium 
HashTable 
324 
Wiggle Sort II 
Solution 

Medium 
Sort 
323 
Number of Connected Components in an Undirected Graph 
Solution 

Medium 

322 
Coin Change 
Solution 

Medium 
DP 
321 
Create Maximum Number 
Solution 

Hard 

320 
Generalized Abbreviation 
Solution 

Medium 
Backtracking, Bit Manipulation 
319 
Bulb Switcher 
Solution 

Medium 
Brainteaser 
318 
Maximum Product of Word Lengths 
Solution 

Medium 

317 
Shortest Distance from All Buildings 
Solution 

Hard 

316 
Remove Duplicate Letters 
Solution 

Hard 
Stack, Recursion, Greedy 
315 
Count of Smaller Numbers After Self 
Solution 

Hard 
Tree 
314 
Binary Tree Vertical Order Traversal 
Solution 

Medium 
HashMap, BFS 
313 
Super Ugly Number 
Solution 

Medium 

312 
Burst Balloons 
Solution 

Hard 
DP 
311 
Sparse Matrix Multiplication 
Solution 

Medium 

310 
Minimum Height Trees 
Solution 

Medium 

309 
Best Time to Buy and Sell Stock with Cooldown 
Solution 

Medium 
DP 
308 
Range Sum Query 2D  Mutable 
Solution 

Hard 
Tree 
307 
Range Sum Query  Mutable 
Solution 

Medium 
Tree 
306 
Additive Number 
Solution 

Medium 

305 
Number of Islands II 
Solution 

Hard 
Union Find 
304 
Range Sum Query 2D  Immutable 
Solution 

Medium 

303 
Range Sum Query  Immutable 
Solution 

Easy 

302 
Smallest Rectangle Enclosing Black Pixels 
Solution 

Hard 
DFS, BFS 
301 
Remove Invalid Parentheses 
Solution 

Hard 
BFS 
300 
Longest Increasing Subsequence 
Solution 

Medium 
DP 
299 
Bulls and Cows 
Solution 

Easy 

298 
Binary Tree Longest Consecutive Sequence 
Solution 

Medium 
Tree 
297 
Serialize and Deserialize Binary Tree 
Solution 

Hard 
BFS 
296 
Best Meeting Point 
Solution 

Hard 

295 
Find Median from Data Stream 
Solution 

Hard 
Heap 
294 
Flip Game II 
Solution 

Medium 
Backtracking 
293 
Flip Game 
Solution 

Easy 

292 
Nim Game 
Solution 

Easy 

291 
Word Pattern II 
Solution 

Hard 
Recursion, Backtracking 
290 
Word Pattern 
Solution 

Easy 
HashMap 
289 
Game of Life 
Solution 
ğŸ“º 
Medium 

288 
Unique Word Abbreviation 
Solution 

Easy 

287 
Find the Duplicate Number 
Solution 

Medium 

286 
Walls and Gates 
Solution 

Medium 
BFS 
285 
Inorder Successor In BST 
Solution 

Medium 
Tree 
284 
Peeking Iterator 
Solution 

Medium 
Design 
283 
Move Zeroes 
Solution 
ğŸ“º 
Easy 

282 
Expression Add Operators 
Solution 

Hard 

281 
Zigzag Iterator 
Solution 

Medium 

280 
Wiggle Sort 
Solution 

Medium 

279 
Perfect Squares 
Solution 

Medium 

278 
First Bad Version 
Solution 
ğŸ“º 
Easy 
Binary Search 
277 
Find the Celebrity 
Solution 

Medium 

276 
Paint Fence 
Solution 

Easy 
DP 
275 
HIndex II 
Solution 

Medium 
Binary Search 
274 
HIndex 
Solution 

Medium 

273 
Integer to English Words 
Solution 

Hard 
Math, String 
272 
Closest Binary Search Tree Value II 
Solution 

Hard 
Stack 
271 
Encode and Decode Strings 
Solution 


Medium 
270 
Closest Binary Search Tree Value 
Solution 


Easy 
269 
Alien Dictionary 
Solution 


Hard 
268 
Missing Number 
Solution 


Easy 
267 
Palindrome Permutation II 
Solution 

Medium 

266 
Palindrome Permutation 
Solution 

Easy 

265 
Paint House II 
Solution 

Hard 
DP 
264 
Ugly Number II 
Solution 

Medium 
DP 
263 
Ugly Number 
Solution 

Easy 

261 
Graph Valid Tree 
Solution 

Medium 

260 
Single Number III 
Solution 

Medium 

259 
3Sum Smaller 
Solution 

Medium 

258 
Add Digits 
Solution 

Easy 

257 
Binary Tree Paths 
Solution 


DFS/Recursion 
256 
Paint House 
Solution 

Medium 
DP 
255 
Verify Preorder Sequence in Binary Search Tree 
Solution 

Medium 
Tree 
254 
Factor Combinations 
Solution 

Medium 
Backtracking 
253 
Meeting Rooms II 
Solution 

Medium 
Heap 
252 
Meeting Rooms 
Solution 

Easy 

251 
Flatten 2D Vector 
Solution 

Medium 

250 
Count Univalue Subtrees 
Solution 

Medium 
DFS 
249 
Group Shifted Strings 
Solution 



248 
Strobogrammatic Number III 
Solution 

Hard 
Recursion, DFS 
247 
Strobogrammatic Number II 
Solution 

Medium 
Recursion 
246 
Strobogrammatic Number 
Solution 

Easy 

245 
Shortest Word Distance III 
Solution 

Medium 

244 
Shortest Word Distance II 
Solution 

Medium 
HashMap 
243 
Shortest Word Distance 
Solution 

Easy 

242 
Valid Anagram 
Solution 

Easy 

241 
Different Ways to Add Parentheses 
Solution 

Medium 
Divide and Conquer 
240 
Search a 2D Matrix II 
Solution 

Medium 
Binary Search 
239 
Sliding Window Maximum 
Solution 

Hard 
Heap 
238 
Product of Array Except Self 
Solution 

Medium 
Array 
237 
Delete Node in a Linked List 
Solution 
ğŸ“º 
Easy 
LinkedList 
236 
Lowest Common Ancestor of a Binary Tree 
Solution 

Medium 
DFS 
235 
Lowest Common Ancestor of a Binary Search Tree 
Solution 

Easy 
DFS 
234 
Palindrome Linked List 
Solution 
ğŸ“º 
Easy 
Linked List 
233 
Number of Digit One 
Solution 

Hard 
Math 
232 
Implement Queue using Stacks 
Solution 

Medium 
Stack, Design 
231 
Power of Two 
Solution 

Easy 

230 
Kth Smallest Element in a BST 
Solution 

Medium 
Tree 
229 
Majority Element II 
Solution 

Medium 

228 
Summary Ranges 
Solution 

Medium 
Array 
227 
Basic Calculator II 
Solution 

Medium 
String 
226 
Invert Binary Tree 
Solution 

Easy 
DFS, recursion 
225 
Implement Stack using Queues 
Solution 

Easy 
Stack, Queue 
224 
Basic Calculator 
Solution 

Hard 

223 
Rectangle Area 
Solution 

Easy 

222 
Count Complete Tree Nodes 
Solution 

Medium 
Recursion 
221 
Maximal Square 
Solution 

Medium 
Recursion 
220 
Contains Duplicate III 
Solution 
ğŸ“º 
Medium 
TreeSet 
219 
Contains Duplicate II 
Solution 
ğŸ“º 
Easy 
HashMap 
218 
The Skyline Problem 
Solution 

Hard 
TreeMap, Design 
217 
Contains Duplicate 
Solution 
ğŸ“º 
Easy 
HashSet 
216 
Combination Sum III 
Solution 

Medium 
Backtracking 
215 
Kth Largest Element in an Array 
Solution 

Medium 
Heap 
214 
Shortest Palindrome 
Solution 

Hard 
KMP 
213 
House Robber II 
Solution 

Medium 
DP 
212 
Word Search II 
Solution 

Hard 
Trie 
211 
Add and Search Word  Data structure design 
Solution 

Medium 
Trie 
210 
Course Schedule II 
Solution 

Medium 

209 
Minimum Size Subarray Sum 
Solution 

Medium 

208 
Implement Trie 
Solution 

Medium 
Trie 
207 
Course Schedule 
Solution 

Medium 

206 
Reverse Linked List 
Solution 
ğŸ“º 
Easy 
Linked List 
205 
Isomorphic Strings 
Solution 

Easy 

204 
Count Primes 
Solution 

Easy 
The Sieve of Eratosthenes 
203 
Remove Linked List Elements 
Solution 

Easy 

202 
Happy Number 
Solution 

Easy 

201 
Bitwise AND of Numbers Range 
Solution 

Medium 
Bit Manipulation 
200 
Number of Islands 
Solution 

Medium 
Union Find, DFS 
199 
Binary Tree Right Side View 
Solution 

Medium 
BFS 
198 
House Robber 
Solution 

Easy 
DP 
191 
Number of 1 Bits 
Solution 

Easy 
Bit Manipulation 
190 
Reverse Bits 
Solution 

Easy 
Bit Manipulation 
189 
Rotate Array 
Solution 
ğŸ“º 
Easy 

188 
Best Time to Buy and Sell Stock IV 
Solution 

Hard 
DP 
187 
Repeated DNA Sequences 
Solution 

Medium 

186 
Reverse Words in a String II 
Solution 

Medium 

179 
Largest Number 
Solution 

Medium 

174 
Dungeon Game 
Solution 

Hard 
DP 
173 
Binary Search Tree Iterator 
Solution 

Medium 
Stack, Design 
172 
Factorial Trailing Zeroes 
Solution 

Easy 

171 
Excel Sheet Column Number 
Solution 

Easy 

170 
Two Sum III  Data structure design 
Solution 

Easy 

169 
Majority Element 
Solution 
ğŸ“º 
Easy 

168 
Excel Sheet Column Title 
Solution 

Easy 

167 
Two Sum II  Input array is sorted 
Java, Javascript


Easy 
Binary Search 
166 
Fraction to Recurring Decimal 
Solution 

Medium 
HashMap 
165 
Compare Version Numbers 
Solution 

Easy 

164 
Maximum Gap 
Solution 

Hard 

163 
Missing Ranges 
Solution 



162 
Find Peak Element 
Solution 

Binary Search 

161 
One Edit Distance 
Solution 



160 
Intersection of Two Linked Lists 
Solution 

Easy 
Linked List 
159 
Longest Substring with At Most Two Distinct Characters 
Solution 

Hard 
String, Sliding Window 
158 
Read N Characters Given Read4 II  Call multiple times 
Solution 

Hard 

157 
Read N Characters Given Read4 
Solution 

Easy 

156 
Binary Tree Upside Down 
Solution 

Medium 
Tree, Recursion 
155 
Min Stack 
Solution 

Easy 
Stack 
154 
Find Minimum in Rotated Sorted Array II 
Solution 

Hard 
Array, Binary Search 
153 
Find Minimum in Rotated Sorted Array 
Solution 

Medium 
Array, Binary Search 
152 
Maximum Product Subarray 
Solution 

Medium 
Array 
151 
Reverse Words in a String 
Solution 

Medium 
String 
150 
Evaluate Reverse Polish Notation 
Solution 

Medium 

149 
Max Points on a Line 
Solution 

Hard 

147 
Insertion Sort List 
Solution 

Medium 
Linked List 
146 
LRU Cache 
Solution 

Hard 
Doubly Linked List, LinkedHashMap 
145 
Binary Tree Postorder Traversal 
Solution 
ğŸ“º 
Hard 
Binary Tree 
144 
Binary Tree Preorder Traversal 
Solution 
ğŸ“º and ğŸ“º

Medium 
Binary Tree 
143 
Reorder List 
Solution 

Medium 

142 
Linked List Cycle II 
Solution 

Medium 
Linked List 
141 
Linked List Cycle 
Solution 
ğŸ“º 
Easy 
Linked List 
140 
Word Break II 
Solution 

Hard 
Backtracking/DFS 
139 
Word Break 
Solution 
ğŸ“º 
Medium 
DP, Pruning 
138 
Copy List with Random Pointer 
Solution 

Medium 
LinkedList, HashMap 
137 
Single Number II 
Solution 

Medium 
Bit Manipulation 
136 
Single Number 
Solution 
ğŸ“º 
Easy 
Bit Manipulation 
135 
Candy 
Solution 

Hard 
Greedy 
134 
Gas Station 
Solution 

Medium 
Greedy 
133 
Clone Graph 
Solution 

Medium 
HashMap, BFS, Graph 
132 
Palindrome Partitioning II 
Solution 

Hard 

131 
Palindrome Partitioning 
Solution 

Medium 

130 
Surrounded Regions 
Solution 

Medium 

129 
Sum Root to Leaf Numbers 
Solution 

Medium 
DFS 
128 
Longest Consecutive Sequence 
Solution 

Hard 
Union Find 
127 
Word Ladder 
Solution 

Medium 
BFS 
126 
Word Ladder II 
Solution 

Hard 
BFS 
125 
Valid Palindrome 
Solution 

Easy 
Two Pointers 
124 
Binary Tree Maximum Path Sum 
Solution 

Hard 
Tree, DFS 
123 
Best Time to Buy and Sell Stock III 
Solution 

Hard 
DP 
122 
Best Time to Buy and Sell Stock II 
Solution 

Easy 
Greedy 
121 
Best Time to Buy and Sell Stock 
Solution 

Easy 

120 
Triangle 
Solution 

Medium 
DP 
119 
Pascal's Triangle II 
Solution 
ğŸ“º 
Easy 

118 
Pascal's Triangle 
Solution 
ğŸ“º 
Easy 

117 
Populating Next Right Pointers in Each Node II 
Solution 

Medium 
BFS 
116 
Populating Next Right Pointers in Each Node 
Solution 

Medium 
BFS 
115 
Distinct Subsequences 
Solution 

Hard 
DP 
114 
Flatten Binary Tree to Linked List 
Solution 

Medium 
Tree 
113 
Path Sum II 
Solution 

Medium 
DFS, Backtracking 
112 
Path Sum 
Solution 

Easy 
DFS 
111 
Minimum Depth of Binary Tree 
Solution 

Easy 
BFS, DFS 
110 
Balanced Binary Tree 
Solution 

Easy 
DFS 
109 
Convert Sorted List to Binary Search Tree 
Solution 

Medium 
DFS, Recursion 
108 
Convert Sorted Array to Binary Search Tree 
Solution 
ğŸ“º 
Easy 
Tree 
107 
Binary Tree Level Order Traversal II 
Solution 

Easy 
BFS 
106 
Construct Binary Tree from Inorder and Postorder Traversal 
Solution 

Medium 
Recursion, Tree 
105 
Construct Binary Tree from Preorder and Inorder Traversal 
Solution 

Medium 
Recursion, Tree 
104 
Maximum Depth of Binary Tree 
Solution 
ğŸ“º 
Easy 
DFS 
103 
Binary Tree Zigzag Level Order Traversal 
Solution 

Medium 
BFS,DFS 
102 
Binary Tree Level Order Traversal 
Solution 
ğŸ“º 
Medium 
BFS 
101 
Symmetric Tree 
Solution 
ğŸ“º 
Easy 
DFS 
100 
Same Tree 
Solution 
ğŸ“º 
Easy 
DFS 
99 
Recover Binary Search Tree 
Solution 

Hard 

98 
Validate Binary Search Tree 
Solution 
ğŸ“º 
Medium 
DFS/Recursion 
97 
Interleaving String 
Solution 

Hard 
DP 
96 
Unique Binary Search Trees 
Solution 

Medium 
Recursion, DP 
95 
Unique Binary Search Trees II 
Solution 

Medium 
Recursion 
94 
Binary Tree Inorder Traversal 
Solution 
ğŸ“º ğŸ“º

Medium 
Binary Tree 
93 
Restore IP Addresses 
Solution 

Medium 
Backtracking 
92 
Reverse Linked List II 
Solution 

Medium 

91 
Decode Ways 
Solution 

Medium 
DP 
90 
Subsets II 
Solution 

Medium 
Backtracking 
89 
Gray Code 
Solution 

Medium 
Bit Manipulation 
88 
Merge Sorted Array 
Solution 

Easy 

87 
Scramble String 
Solution 

Hard 
Recursion 
86 
Partition List 
Solution 

Medium 
Linked List 
85 
Maximal Rectangle 
Solution 

Hard 
DP 
84 
Largest Rectangle in Histogram 
Solution 

Hard 
Array, Stack 
83 
Remove Duplicates from Sorted List 
Solution 

Easy 
Linked List 
82 
Remove Duplicates from Sorted List II 
Solution 

Medium 
Linked List 
81 
Search in Rotated Sorted Array II 
Solution 

Medium 
Binary Search 
80 
Remove Duplicates from Sorted Array II 
Solution 

Medium 

79 
Word Search 
Solution 

Medium 
Backtracking, DFS 
78 
Subsets 
Solution 

Medium 
Backtracking 
77 
Combinations 
Solution 

Medium 
Backtracking 
76 
Minimum Window Substring 
Solution 

Hard 
Two Pointers 
75 
Sort Colors 
Solution 

Medium 
Two Pointers 
74 
Search a 2D Matrix 
Solution 

Medium 
Binary Search 
73 
Set Matrix Zeroes 
Solution 

Medium 

72 
Edit Distance 
Solution 

Hard 

71 
Simplify Path 
Solution 

Medium 
Stack 
70 
Climbing Stairs 
Solution 
ğŸ“º 
Easy 
DP 
69 
Sqrt(x) 
Solution 

Easy 

68 
Text Justification 
Solution 

Hard 

67 
Add Binary 
Solution 

Easy 

66 
Plus One 
Solution 
ğŸ“º 
Easy 

65 
Valid Number 
Solution 

Hard 

64 
Minimum Path Sum 
Solution 

Medium 
DP 
63 
Unique Paths II 
Solution 

Medium 
DP 
62 
Unique Paths 
Solution 

Medium 
DP 
61 
Rotate List 
Solution 

Medium 
Linked List 
60 
Permutation Sequence 
Solution 

Medium 
Math, Backtracking 
59 
Spiral Matrix II 
Solution 
ğŸ“º 
Medium 

58 
Length of Last Word 
Solution 

Easy 

57 
Insert Intervals 
Solution 

Hard 
Array, Sort 
56 
Merge Intervals 
Solution 

Medium 
Array, Sort 
55 
Jump Game 
Solution 

Medium 
Greedy 
54 
Spiral Matrix 
Solution 
ğŸ“º 
Medium 
Array 
53 
Maximum Subarray 
Solution 

Easy 
Array 
52 
NQueens II 
Solution 

Hard 
Backtracking 
51 
NQueens 
Solution 

Hard 

50 
Pow(x, n) 
Solution 

Medium 

49 
Group Anagrams 
Solution 

Medium 
HashMap 
48 
Rotate Image 
Solution 
ğŸ“º 
Medium 
Array 
47 
Permutations II 
Solution 

Medium 
Backtracking 
46 
Permutations 
Solution 

Medium 
Backtracking 
45 
Jump Game II 
Solution 

Hard 
Array, Greedy 
44 
Wildcard Matching 
Solution 

Hard 
Backtracking, DP, Greedy, String 
43 
Multiply Strings 
Solution 

Medium 
Array, String 
42 
Trapping Rain Water 
Solution 

Hard 

41 
First Missing Positive 
Solution 

Hard 
Array 
40 
Combination Sum II 
Solution 

Medium 
Backtracking 
39 
Combination Sum 
Solution 

Medium 
Backtracking 
38 
Count and Say 
Solution 

Easy 
Recursion, LinkedList 
37 
Sudoku Solver 
Solution 

Hard 

36 
Valid Sudoku 
Solution 

Medium 

35 
Search Insert Position 
Solution 

Easy 
Array 
34 
Search for a Range 
Solution 

Medium 
Array, Binary Search 
33 
Search in Rotated Sorted Array 
Solution 

Medium 
Binary Search 
32 
Longest Valid Parentheses 
Solution 

Hard 
Stack, DP 
31 
Next Permutation 
Solution, C++


Medium 
Array 
30 
Substring with Concatenation of All Words 
Solution 

Hard 
HashMap 
29 
Divide Two Integers 
Solution 

Medium 

28 
Implement strStr() 
Solution 

Easy 
String 
27 
Remove Element 
Solution 

Easy 

26 
Remove Duplicates from Sorted Array 
Solution 
ğŸ“º 
Easy 
Array 
25 
Reverse Nodes in kGroup 
Solution 

Hard 
Recursion, LinkedList 
24 
Swap Nodes in Pairs 
Solution 

Medium 
Recursion, LinkedList 
23 
Merge k Sorted Lists 
Solution 
ğŸ“º 
Hard 
Heap 
22 
Generate Parentheses 
Solution 

Medium 
Backtracking 
21 
Merge Two Sorted Lists 
Solution 
ğŸ“º 
Easy 
Recursion 
20 
Valid Parentheses 
Solution 
ğŸ“º 
Easy 
Stack 
19 
Remove Nth Node From End of List 
Solution 
ğŸ“º 
Medium 
Linked List 
18 
4 Sum 
Solution 

Medium 
Two Pointers 
17 
Letter Combinations of a Phone Number 
Solution 

Medium 
Backtracking 
16 
3Sum Closest 
Solution 

Medium 
Two Pointers 
15 
3Sum 
Solution, C++

ğŸ“º 
Medium 
Two Pointers, Binary Search 
14 
Longest Common Prefix 
Solution 
ğŸ“º 
Easy 

13 
Roman to Integer 
Solution 

Easy 
Math, String 
12 
Integer to Roman 
Solution 

Medium 
Math, String 
11 
Container With Most Water 
Solution 

Medium 

10 
Regular Expression Matching 
Java, Javascript


Hard 
DP 
9 
Palindrome Number 
Java, C++


Easy 

8 
String to Integer (atoi) 
Solution 

Medium 

7 
Reverse Integer 
Solution, C++

ğŸ“º 
Easy 

6 
ZigZag Conversion 
Solution 

Easy 

5 
Longest Palindromic Substring 
Solution 

Medium 

4 
Median of Two Sorted Arrays 
Solution, C++


Hard 
Divide and Conquer 
3 
Longest Substring Without Repeating Characters 
Solution, C++


Medium 
HashMap, Sliding Window 
2 
Add Two Numbers 
Solution 

Medium 
LinkedList 
1 
Two Sum 
Java, C++, Javascript

ğŸ“º 
Easy 
HashMap 