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My LeetCode Solutions!

Contributing

Contributions are very welcome!

If you see an problem that you’d like to see fixed, the best way to make it happen is to help out by submitting a pull request implementing it. Refer to the CONTRIBUTING.md file for more details about the workflow.

You can also ask for problem solving ideas and discuss in GitHub issues directly.

INDEX

Learn

Array and String

# Title Solutions Difficulty Tag
14 Longest Common Prefix Java & Python Easy Introduction to String
26 Remove Duplicates from Sorted Array Java & Python Easy Conclusion
27 Remove Element Java & Python Easy Two-Pointer Technique
28 Implement strStr() Java & Python Easy Introduction to String
54 Spiral Matrix Java & Python Medium Introduction to 2D Array
66 Plus One Java & Python Easy Introduction to Array
67 Add Binary Java & Python Easy Introduction to String
118 Pascal’s Triangle Java & Python Easy Introduction to 2D Array
119 Pascal’s Triangle II Java & Python Easy Conclusion
151 Reverse Words in a String Java & Python Medium Conclusion
167 Two Sum II - Input array is sorted Java & Python Easy Two-Pointer Technique
189 Rotate Array Java & Python Easy Conclusion
209 Minimum Size Subarray Sum Java & Python Medium Two-Pointer Technique
283 Move Zeroes Java & Python Easy Conclusion
344 Reverse String Java & Python Easy Two-Pointer Technique
485 Max Consecutive Ones Java & Python Easy Two-Pointer Technique
498 Diagonal Traverse Java & Python Medium Introduction to 2D Array
557 Reverse Words in a String III Java & Python Easy Conclusion
561 Array Partition I Java & Python Easy Two-Pointer Technique
724 Find Pivot Index Java & Python Easy Introduction to Array
747 Largest Number Greater Than Twice of Others Java & Python Easy Introduction to Array

Queue & Stack

# Title Solutions Difficulty Tag
20 Valid Parentheses Java & Python Easy Stack: Last-in-first-out Data Structure
133 Clone Graph Java & Python Medium Stack and DFS
150 Evaluate Reverse Polish Notation Java & Python Medium Stack: Last-in-first-out Data Structure
155 Min Stack Java & Python Easy Stack: Last-in-first-out Data Structure
200 Number of Islands Java & Python Medium Queue and BFS
225 Implement Stack using Queues Java & Python Easy Conclusion
232 Implement Queue using Stacks Java & Python Easy Conclusion
279 Perfect Squares Java & Python Medium Queue and BFS
394 Decode String Java & Python Medium Conclusion
494 Target Sum Java & Python Medium Stack and DFS
542 01 Matrix Java & Python Medium Conclusion
622 Design Circular Queue Java & Python Medium Queue: First-in-first-out Data Structure
733 Flood Fill Java & Python Easy Conclusion
739 Daily Temperatures Java & Python Medium Stack: Last-in-first-out Data Structure
752 Open the Lock Java & Python Medium Queue and BFS
841 Keys and Rooms Java & Python Medium Conclusion

Linked List

# Title Solutions Difficulty Tag
2 Add Two Numbers Java & Python Medium Conclusion
19 Remove Nth Node From End of List Java & Python Medium Two Pointer Technique
21 Merge Two Sorted Lists Java & Python Easy Conclusion
61 Rotate List Java & Python Medium Conclusion
135 Copy List with Random Pointer Java & Python Medium Conclusion
141 Linked List Cycle Java & Python Easy Two Pointer Technique
142 Linked List Cycle II Java & Python Medium Two Pointer Technique
160 Intersection of Two Linked Lists Java & Python Easy Two Pointer Technique
203 Remove Linked List Elements Java & Python Easy Classic Problems
206 Reverse Linked List Java & Python Easy Classic Problems
234 Palindrome Linked List Java & Python Easy Classic Problems
328 Odd Even Linked List Java & Python Medium Classic Problems
430 Flatten a Multilevel Doubly Linked List Java & Python Medium Conclusion
707 Design Linked List Java & Python Easy Singly Linked List

Hash Table

# Title Solutions Difficulty Tag
1 Two Sum Java & Python Easy Practical Application - Hash Map
3 Longest Substring Without Repeating Characters Java & Python Medium Conclusion
36 Valid Sudoku Java & Python Medium Practical Application - Design the Key
49 Group Anagrams Java & Python Medium Practical Application - Design the Key
136 Single Number Java & Python Easy Practical Application - Hash Set
202 Happy Number Java & Python Easy Practical Application - Hash Set
205 Isomorphic Strings Java & Python Easy Practical Application - Hash Map
217 Contains Duplicate Java & Python Easy Practical Application - Hash Set
219 Contains Duplicate II Java & Python Easy Practical Application - Hash Map
347 Top K Frequent Elements Java & Python Medium Conclusion
349 Intersection of Two Arrays Java & Python Easy Practical Application - Hash Set
350 Intersection of Two Arrays II Java & Python Easy Practical Application - Hash Map
380 Insert Delete GetRandom O(1) Java & Python Medium Conclusion
387 First Unique Character in a String Java & Python Easy Practical Application - Hash Map
454 4Sum II Java & Python Medium Conclusion
599 Minimum Index Sum of Two Lists Java & Python Easy Practical Application - Hash Map
652 Find Duplicate Subtrees Java & Python Medium Practical Application - Design the Key
705 Design HashSet Java & Python Easy Design a Hash Table
706 Design HashMap Java & Python Easy Design a Hash Table
771 Jewels and Stones Java & Python Easy Conclusion
# Title Solutions Difficulty Tag
4 Median of Two Sorted Arrays Java & Python Hard More Practices II
33 Search in Rotated Sorted Array Java & Python Medium Template I
34 Find First and Last Position of Element in Sorted Array Java & Python Medium Template III
50 Pow(x, n) Java & Python Medium Conclusion
69 Sqrt(x) Java & Python Easy Template I
153 Find Minimum in Rotated Sorted Array Java & Python Medium Template II
154 Find Minimum in Rotated Sorted Array II Java & Python Hard More Practices
162 Find Peak Element Java & Python Medium Template II
167 Two Sum II - Input array is sorted Java & Python Easy More Practices
278 First Bad Version Java & Python Easy Template II
287 Find the Duplicate Number Java & Python Medium More Practices II
349 Intersection of Two Arrays Java & Python Easy More Practices
350 Intersection of Two Arrays II Java & Python Easy More Practices
367 Valid Perfect Square Java & Python Easy Conclusion
374 Guess Number Higher or Lower Java & Python Easy Template I
410 Split Array Largest Sum Java & Python Hard More Practices II
658 Find K Closest Elements Java & Python Medium Template III
704 Binary Search Java & Python Easy Background
719 Find K-th Smallest Pair Distance Java & Python Hard More Practices II
744 Find Smallest Letter Greater Than Target Java & Python Easy Conclusion

Binary Tree

# Title Solutions Difficulty Tag
94 Binary Tree Inorder Traversal Java & Python Medium Traverse A Tree
101 Symmetric Tree Java & Python Easy Solve Tree Problems Recursively
102 Binary Tree Level Order Traversal Java & Python Medium Traverse A Tree
104 Maximum Depth of Binary Tree Java & Python Easy Solve Tree Problems Recursively
105 Construct Binary Tree from Preorder and Inorder Traversal Java & Python Medium Conclusion
106 Construct Binary Tree from Inorder and Postorder Traversal Java & Python Medium Conclusion
112 Path Sum Java & Python Easy Solve Tree Problems Recursively
116 Populating Next Right Pointers in Each Node Java & Python Medium Conclusion
117 Populating Next Right Pointers in Each Node II Java & Python Medium Conclusion
144 Binary Tree Preorder Traversal Java & Python Medium Traverse A Tree
145 Binary Tree Postorder Traversal Java & Python Hard Traverse A Tree
236 Lowest Common Ancestor of a Binary Tree Java & Python Medium Conclusion
297 Serialize and Deserialize Binary Tree Java & Python Medium Conclusion

Binary Search Tree

# Title Solutions Difficulty Tag
98 Validate Binary Search Tree Java & Python Medium Introduction to BST
108 Convert Sorted Array to Binary Search Tree Java & Python Easy Appendix: Height-balanced BST
110 Balanced Binary Tree Java & Python Easy Appendix: Height-balanced BST
173 Binary Search Tree Iterator Java & Python Medium Introduction to BST
220 Contains Duplicate III Java & Python Medium Conclusion
235 Lowest Common Ancestor of a Binary Search Tree Java & Python Easy Conclusion
450 Delete Node in a BST Java & Python Medium Basic Operations in BST
700 Search in a Binary Search Tree Java & Python Easy Basic Operations in BST
701 Insert into a Binary Search Tree Java & Python Medium Basic Operations in BST
703 Kth Largest Element in a Stream Java & Python Easy Conclusion

N-ary Tree

# Title Solutions Difficulty Tag
429 N-ary Tree Level Order Traversal Java & Python Easy Traversal
559 Maximum Depth of N-ary Tree Java & Python Easy Recursion
589 N-ary Tree Preorder Traversal Java & Python Easy Traversal
590 N-ary Tree Postorder Traversal Java & Python Easy Traversal

Trie (Prefix Tree)

# Title Solutions Difficulty Tag
208 Implement Trie (Prefix Tree) Java & Python Medium Basic Operations
211 Add and Search Word - Data structure design Java & Python Medium Practical Application I
212 Word Search II Java & Python Hard Practical Application II
336 Palindrome Pairs Java & Python Hard Practical Application II
421 Maximum XOR of Two Numbers in an Array Java & Python Medium Practical Application II
648 Replace Words Java & Python Medium Practical Application I
677 Map Sum Pairs Java & Python Medium Practical Application I

Decision Tree

# Title Solutions Difficulty Tag
### Calculate Entropy Java & Python Easy Implementation
### Calculate Maximum Information Gain Java & Python Easy Implementation

Recursion I

# Title Solutions Difficulty Tag
21 Merge Two Sorted Lists Java & Python Easy Conclusion
24 Swap Nodes in Pairs Java & Python Medium Principle of Recursion
50 Pow(x, n) Java & Python Medium Complexity Analysis
70 Climbing Stairs Java & Python Easy Memoization
95 Unique Binary Search Trees II Java & Python Medium Conclusion
104 Maximum Depth of Binary Tree Java & Python Easy Complexity Analysis
118 Pascal’s Triangle Java & Python Easy Recurrence Relation
119 Pascal’s Triangle II Java & Python Easy Recurrence Relation
206 Reverse Linked List Java & Python Easy Recurrence Relation
344 Reverse String Java & Python Easy Principle of Recursion
509 Fibonacci Number Java & Python Easy Memoization
779 K-th Symbol in Grammar Java & Python Medium Conclusion

Recursion II

# Title Solutions Difficulty Tag
17 Letter Combinations of a Phone Number Java & Python Medium Conclusion
22 Generate Parentheses Java & Python Medium Recursion to Iteration
37 Sudoku Solver Java & Python Hard Backtracking
46 Permutations Java & Python Medium Conclusion
52 N-Queens II Java & Python Hard Backtracking
77 Combinations Java & Python Medium Backtracking
84 Largest Rectangle in Histogram Java & Python Hard Conclusion
94 Binary Tree Inorder Traversal Java & Python Medium Recursion to Iteration
98 Validate Binary Search Tree Java & Python Medium Divide and Conquer
100 Same Tree Java & Python Easy Recursion to Iteration
102 Binary Tree Level Order Traversal Java & Python Medium Recursion to Iteration
218 The Skyline Problem Java & Python Hard Conclusion
240 Search a 2D Matrix II Java & Python Medium Divide and Conquer
912 Sort an Array Java & Python Medium Divide and Conquer

Concurrency

# Title Solutions Difficulty Tag
1114 Print in Order Java & Python Easy Concurrency
1115 Print FooBar Alternately Java & Python Medium Concurrency
1116 Print Zero Even Odd Java & Python Medium Concurrency
1117 Building H2O Java & Python Medium Concurrency
1195 Fizz Buzz Multithreaded Java & Python Medium Concurrency
1226 The Dining Philosophers Java & Python Medium Concurrency

Others

# Title Solutions Difficulty Tag
6 ZigZag Conversion Java & Python Medium Others
9 Palindrome Number Java & Python Easy Others
12 Integer to Roman Java & Python Medium Others
16 3Sum Closest Java & Python Medium Others
18 4Sum Java & Python Medium Others
25 Reverse Nodes in k-Group Java & Python Hard Others
30 Substring with Concatenation of All Words Java & Python Hard Others
31 Next Permutation Java & Python Medium Others
32 Longest Valid Parentheses Java & Python Hard Others
35 Search Insert Position Java & Python Easy Others
39 Combination Sum Java & Python Medium Others
40 Combination Sum II Java & Python Medium Others
43 Multiply Strings Java & Python Medium Others
45 Jump Game II Java & Python Hard Others
47 Permutations II Java & Python Medium Others
51 N-Queens Java & Python Hard Others
57 Insert Interval Java & Python Hard Others
58 Length of Last Word Java & Python Easy Others
59 Spiral Matrix II Java & Python Medium Others
60 Permutation Sequence Java & Python Medium Others
63 Unique Paths II Java & Python Medium Others
64 Minimum Path Sum Java & Python Medium Others
65 Valid Number Java & Python Hard Others
68 Text Justification Java & Python Hard Others
71 Simplify Path Java & Python Medium Others
72 Edit Distance Java & Python Hard Others
74 Search a 2D Matrix Java & Python Medium Others
80 Remove Duplicates from Sorted Array II Java & Python Medium Others
81 Search in Rotated Sorted Array II Java & Python Medium Others
82 Remove Duplicates from Sorted List II Java & Python Medium Others
83 Remove Duplicates from Sorted List Java & Python Easy Others
85 Maximal Rectangle Java & Python Hard Others
86 Partition List Java & Python Medium Others
87 Scramble String Java & Python Hard Others
89 Gray Code Java & Python Medium Others
90 Subsets II Java & Python Medium Others
92 Reverse Linked List II Java & Python Medium Others
93 Restore IP Addresses Java & Python Medium Others
96 Unique Binary Search Trees Java & Python Medium Others
97 Interleaving String Java & Python Hard Others
99 Recover Binary Search Tree Java & Python Hard Others
107 Binary Tree Level Order Traversal II Java & Python Easy Others
109 Convert Sorted List to Binary Search Tree Java & Python Medium Others
111 Minimum Depth of Binary Tree Java & Python Easy Others
113 Path Sum II Java & Python Medium Others
114 Flatten Binary Tree to Linked List Java & Python Medium Others
115 Distinct Subsequences Java & Python Hard Others
120 Triangle Java & Python Medium Others
123 Best Time to Buy and Sell Stock III Java & Python Hard Others
126 Word Ladder II Java & Python Hard Others
129 Sum Root to Leaf Numbers Java & Python Medium Others
132 Palindrome Partitioning II Java & Python Hard Others
134 Gas Station Java & Python Medium Others
135 Candy Java & Python Hard Others
137 Single Number II Java & Python Medium Others
143 Reorder List Java & Python Medium Others
147 Insertion Sort List Java & Python Medium Others
164 Maximum Gap Java & Python Hard Others
165 Compare Version Numbers Java & Python Medium Others
168 Excel Sheet Column Title Java & Python Easy Others
174 Dungeon Game Java & Python Hard Others
187 Repeated DNA Sequences Java & Python Medium Others
188 Best Time to Buy and Sell Stock IV Java & Python Hard Others
199 Binary Tree Right Side View Java & Python Medium Others
201 Bitwise AND of Numbers Range Java & Python Medium Others
213 House Robber II Java & Python Medium Others
214 Shortest Palindrome Java & Python Hard Others
216 Combination Sum III Java & Python Medium Others
221 Maximal Square Java & Python Medium Others
222 Count Complete Tree Nodes Java & Python Medium Others
223 Rectangle Area Java & Python Medium Others
224 Basic Calculator Java & Python Hard Others
226 Invert Binary Tree Java & Python Easy Others
228 Summary Ranges Java & Python Medium Others
229 Majority Element II Java & Python Medium Others
231 Power of Two Java & Python Easy Others
233 Number of Digit One Java & Python Hard Others
241 Different Ways to Add Parentheses Java & Python Medium Others
257 Binary Tree Paths Java & Python Easy Others
258 Add Digits Java & Python Easy Others
260 Single Number III Java & Python Medium Others
263 Ugly Number Java & Python Easy Others
264 Ugly Number II Java & Python Medium Others
273 Integer to English Words Java & Python Hard Others
274 H-Index Java & Python Medium Others
275 H-Index II Java & Python Medium Others
282 Expression Add Operators Java & Python Hard Others
284 Peeking Iterator Java & Python Medium Others
290 Word Pattern Java & Python Easy Others
292 Nim Game Java & Python Easy Others
299 Bulls and Cows Java & Python Easy Others
303 Range Sum Query - Immutable Java & Python Easy Others
304 Range Sum Query 2D - Immutable Java & Python Medium Others
306 Additive Number Java & Python Medium Others
307 Range Sum Query - Mutable Java & Python Medium Others
310 Minimum Height Trees Java & Python Medium Others
313 Super Ugly Number Java & Python Medium Others
316 Remove Duplicate Letters Java & Python Hard Others
318 Maximum Product of Word Lengths Java & Python Medium Others
319 Bulb Switcher Java & Python Medium Others
321 Create Maximum Number Java & Python Hard Others
327 Count of Range Sum Java & Python Hard Others
330 Patching Array Java & Python Hard Others
331 Verify Preorder Serialization of a Binary Tree Java & Python Medium Others
332 Reconstruct Itinerary Java & Python Medium Others
335 Self Crossing Java & Python Hard Others
337 House Robber III Java & Python Medium Others
338 Counting Bits Java & Python Medium Others
342 Power of Four Java & Python Easy Others
343 Integer Break Java & Python Medium Others
345 Reverse Vowels of a String Java & Python Easy Others
352 Data Stream as Disjoint Intervals Java & Python Hard Others
354 Russian Doll Envelopes Java & Python Hard Others
355 Design Twitter Java & Python Medium Others
357 Count Numbers with Unique Digits Java & Python Medium Others
363 Max Sum of Rectangle No Larger Than K Java & Python Hard Others
365 Water and Jug Problem Java & Python Medium Others
368 Largest Divisible Subset Java & Python Medium Others
372 Super Pow Java & Python Medium Others
373 Find K Pairs with Smallest Sums Java & Python Medium Others
375 Guess Number Higher or Lower II Java & Python Medium Others
376 Wiggle Subsequence Java & Python Medium Others
377 Combination Sum IV Java & Python Medium Others
381 Insert Delete GetRandom O(1) - Duplicates allowed Java & Python Hard Others
382 Linked List Random Node Java & Python Medium Others
383 Ransom Note Java & Python Easy Others
385 Mini Parser Java & Python Medium Others
386 Lexicographical Numbers Java & Python Medium Others
388 Longest Absolute File Path Java & Python Medium Others
389 Find the Difference Java & Python Easy Others
390 Elimination Game Java & Python Medium Others
391 Perfect Rectangle Java & Python Hard Others
392 Is Subsequence Java & Python Easy Others
393 UTF-8 Validation Java & Python Medium Others
395 Longest Substring with At Least K Repeating Characters Java & Python Medium Others
396 Rotate Function Java & Python Medium Others
397 Integer Replacement Java & Python Medium Others
398 Random Pick Index Java & Python Medium Others
399 Evaluate Division Java & Python Medium Others
400 Nth Digit Java & Python Medium Others
401 Binary Watch Java & Python Easy Others
402 Remove K Digits Java & Python Medium Others
403 Frog Jump Java & Python Hard Others
404 Sum of Left Leaves Java & Python Easy Others
405 Convert a Number to Hexadecimal Java & Python Easy Others
407 Trapping Rain Water II Java & Python Hard Others
409 Longest Palindrome Java & Python Easy Others
413 Arithmetic Slices Java & Python Medium Others
414 Third Maximum Number Java & Python Easy Others
415 Add Strings Java & Python Easy Others
416 Partition Equal Subset Sum Java & Python Medium Others
417 Pacific Atlantic Water Flow Java & Python Medium Others
419 Battleships in a Board Java & Python Medium Others
420 Strong Password Checker Java & Python Hard Others
423 Reconstruct Original Digits from English Java & Python Medium Others
424 Longest Repeating Character Replacement Java & Python Medium Others
427 Construct Quad Tree Java & Python Medium Others
432 All O`one Data Structure Java & Python Hard Others
433 Minimum Genetic Mutation Java & Python Medium Others
434 Number of Segments in a String Java & Python Easy Others
435 Non-overlapping Intervals Java & Python Medium Others
436 Find Right Interval Java & Python Medium Others
437 Path Sum III Java & Python Easy Others
438 Find All Anagrams in a String Java & Python Medium Others
440 K-th Smallest in Lexicographical Order Java & Python Hard Others
441 Arranging Coins Java & Python Easy Others
442 Find All Duplicates in an Array Java & Python Medium Others
443 String Compression Java & Python Easy Others
445 Add Two Numbers II Java & Python Medium Others
446 Arithmetic Slices II - Subsequence Java & Python Hard Others
447 Number of Boomerangs Java & Python Easy Others
448 Find All Numbers Disappeared in an Array Java & Python Easy Others
449 Serialize and Deserialize BST Java & Python Medium Others
451 Sort Characters By Frequency Java & Python Medium Others
452 Minimum Number of Arrows to Burst Balloons Java & Python Medium Others
453 Minimum Moves to Equal Array Elements Java & Python Easy Others
455 Assign Cookies Java & Python Easy Others
456 132 Pattern Java & Python Medium Others
457 Circular Array Loop Java & Python Medium Others
458 Poor Pigs Java & Python Hard Others
459 Repeated Substring Pattern Java & Python Easy Others
460 LFU Cache Java & Python Hard Others
462 Minimum Moves to Equal Array Elements II Java & Python Medium Others
463 Island Perimeter Java & Python Easy Others
464 Can I Win Java & Python Medium Others
466 Count The Repetitions Java & Python Hard Others
467 Unique Substrings in Wraparound String Java & Python Medium Others
468 Validate IP Address Java & Python Medium Others
470 Implement Rand10() Using Rand7() Java & Python Medium Others
472 Concatenated Words Java & Python Hard Others
473 Matchsticks to Square Java & Python Medium Others
474 Ones and Zeroes Java & Python Medium Others
475 Heaters Java & Python Easy Others
476 Number Complement Java & Python Easy Others
477 Total Hamming Distance Java & Python Medium Others
478 Generate Random Point in a Circle Java & Python Medium Others
479 Largest Palindrome Product Java & Python Hard Others
480 Sliding Window Median Java & Python Hard Others
481 Magical String Java & Python Medium Others
482 License Key Formatting Java & Python Easy Others
483 Smallest Good Base Java & Python Hard Others
486 Predict the Winner Java & Python Medium Others
488 Zuma Game Java & Python Hard Others
491 Increasing Subsequences Java & Python Medium Others
492 Construct the Rectangle Java & Python Easy Others
493 Reverse Pairs Java & Python Hard Others
495 Teemo Attacking Java & Python Medium Others
496 Next Greater Element I Java & Python Easy Others
497 Random Point in Non-overlapping Rectangles Java & Python Medium Others
500 Keyboard Row Java & Python Easy Others
501 Find Mode in Binary Search Tree Java & Python Easy Others
502 IPO Java & Python Hard Others
503 Next Greater Element II Java & Python Medium Others
504 Base 7 Java & Python Easy Others
506 Relative Ranks Java & Python Easy Others
507 Perfect Number Java & Python Easy Others
508 Most Frequent Subtree Sum Java & Python Medium Others
513 Find Bottom Left Tree Value Java & Python Medium Others
514 Freedom Trail Java & Python Hard Others
515 Find Largest Value in Each Tree Row Java & Python Medium Others
516 Longest Palindromic Subsequence Java & Python Medium Others
517 Super Washing Machines Java & Python Hard Others
518 Coin Change 2 Java & Python Medium Others
519 Random Flip Matrix Java & Python Medium Others
520 Detect Capital Java & Python Easy Others
521 Longest Uncommon Subsequence I Java & Python Easy Others
522 Longest Uncommon Subsequence II Java & Python Medium Others
523 Continuous Subarray Sum Java & Python Medium Others
524 Longest Word in Dictionary through Deleting Java & Python Medium Others
525 Contiguous Array Java & Python Medium Others
526 Beautiful Arrangement Java & Python Medium Others
528 Random Pick with Weight Java & Python Medium Others
529 Minesweeper Java & Python Medium Others
530 Minimum Absolute Difference in BST Java & Python Easy Others
532 K-diff Pairs in an Array Java & Python Easy Others
535 Encode and Decode TinyURL Java & Python Medium Others
537 Complex Number Multiplication Java & Python Medium Others
538 Convert BST to Greater Tree Java & Python Easy Others
539 Minimum Time Difference Java & Python Medium Others
540 Single Element in a Sorted Array Java & Python Medium Others
541 Reverse String II Java & Python Easy Others
543 Diameter of Binary Tree Java & Python Easy Others
546 Remove Boxes Java & Python Hard Others
551 Student Attendance Record I Java & Python Easy Others
552 Student Attendance Record II Java & Python Hard Others
553 Optimal Division Java & Python Medium Others
554 Brick Wall Java & Python Medium Others
556 Next Greater Element III Java & Python Medium Others
558 Quad Tree Intersection Java & Python Easy Others
560 Subarray Sum Equals K Java & Python Medium Others
563 Binary Tree Tilt Java & Python Easy Others
564 Find the Closest Palindrome Java & Python Hard Others
565 Array Nesting Java & Python Medium Others
566 Reshape the Matrix Java & Python Easy Others
567 Permutation in String Java & Python Medium Others
572 Subtree of Another Tree Java & Python Easy Others
575 Distribute Candies Java & Python Easy Others
576 Out of Boundary Paths Java & Python Medium Others
581 Shortest Unsorted Continuous Subarray Java & Python Easy Others
583 Delete Operation for Two Strings Java & Python Medium Others
587 Erect the Fence Java & Python Hard Others
591 Tag Validator Java & Python Hard Others
592 Fraction Addition and Subtraction Java & Python Medium Others
593 Valid Square Java & Python Medium Others
594 Longest Harmonious Subsequence Java & Python Easy Others
598 Range Addition II Java & Python Easy Others
600 Non-negative Integers without Consecutive Ones Java & Python Hard Others
605 Can Place Flowers Java & Python Easy Others
606 Construct String from Binary Tree Java & Python Easy Others
609 Find Duplicate File in System Java & Python Medium Others
611 Valid Triangle Number Java & Python Medium Others
617 Merge Two Binary Trees Java & Python Easy Others
623 Add One Row to Tree Java & Python Medium Others
628 Maximum Product of Three Numbers Java & Python Easy Others
629 K Inverse Pairs Array Java & Python Hard Others
630 Course Schedule III Java & Python Hard Others
632 Smallest Range Covering Elements from K Lists Java & Python Hard Others
633 Sum of Square Numbers Java & Python Easy Others
636 Exclusive Time of Functions Java & Python Medium Others
637 Average of Levels in Binary Tree Java & Python Easy Others
638 Shopping Offers Java & Python Medium Others
639 Decode Ways II Java & Python Hard Others
640 Solve the Equation Java & Python Medium Others
641 Design Circular Deque Java & Python Medium Others
643 Maximum Average Subarray I Java & Python Easy Others
645 Set Mismatch Java & Python Easy Others
646 Maximum Length of Pair Chain Java & Python Medium Others
647 Palindromic Substrings Java & Python Medium Others
649 Dota2 Senate Java & Python Medium Others
650 2 Keys Keyboard Java & Python Medium Others
653 Two Sum IV - Input is a BST Java & Python Easy Others
654 Maximum Binary Tree Java & Python Medium Others
655 Print Binary Tree Java & Python Medium Others
657 Robot Return to Origin Java & Python Easy Others
659 Split Array into Consecutive Subsequences Java & Python Medium Others
661 Image Smoother Java & Python Easy Others
662 Maximum Width of Binary Tree Java & Python Medium Others
664 Strange Printer Java & Python Hard Others
665 Non-decreasing Array Java & Python Easy Others
667 Beautiful Arrangement II Java & Python Medium Others
668 Kth Smallest Number in Multiplication Table Java & Python Hard Others
669 Trim a Binary Search Tree Java & Python Easy Others
670 Maximum Swap Java & Python Medium Others
671 Second Minimum Node In a Binary Tree Java & Python Easy Others
672 Bulb Switcher II Java & Python Medium Others
673 Number of Longest Increasing Subsequence Java & Python Medium Others
674 Longest Continuous Increasing Subsequence Java & Python Easy Others
675 Cut Off Trees for Golf Event Java & Python Hard Others
676 Implement Magic Dictionary Java & Python Medium Others
678 Valid Parenthesis String Java & Python Medium Others
679 24 Game Java & Python Hard Others
680 Valid Palindrome II Java & Python Easy Others
682 Baseball Game Java & Python Easy Others
684 Redundant Connection Java & Python Medium Others
685 Redundant Connection II Java & Python Hard Others
686 Repeated String Match Java & Python Easy Others
687 Longest Univalue Path Java & Python Easy Others
688 Knight Probability in Chessboard Java & Python Medium Others
689 Maximum Sum of 3 Non-Overlapping Subarrays Java & Python Hard Others
690 Employee Importance Java & Python Easy Others
691 Stickers to Spell Word Java & Python Hard Others
692 Top K Frequent Words Java & Python Medium Others
693 Binary Number with Alternating Bits Java & Python Easy Others
695 Max Area of Island Java & Python Medium Others
696 Count Binary Substrings Java & Python Easy Others
697 Degree of an Array Java & Python Easy Others
698 Partition to K Equal Sum Subsets Java & Python Medium Others
699 Falling Squares Java & Python Hard Others
709 To Lower Case Java & Python Easy Others
710 Random Pick with Blacklist Java & Python Hard Others
712 Minimum ASCII Delete Sum for Two Strings Java & Python Medium Others
713 Subarray Product Less Than K Java & Python Medium Others
714 Best Time to Buy and Sell Stock with Transaction Fee Java & Python Medium Others
715 Range Module Java & Python Hard Others
717 1-bit and 2-bit Characters Java & Python Easy Others
718 Maximum Length of Repeated Subarray Java & Python Medium Others
720 Longest Word in Dictionary Java & Python Easy Others
721 Accounts Merge Java & Python Medium Others
722 Remove Comments Java & Python Medium Others
725 Split Linked List in Parts Java & Python Medium Others
726 Number of Atoms Java & Python Hard Others
728 Self Dividing Numbers Java & Python Easy Others
729 My Calendar I Java & Python Medium Others
730 Count Different Palindromic Subsequences Java & Python Hard Others
731 My Calendar II Java & Python Medium Others
732 My Calendar III Java & Python Hard Others
735 Asteroid Collision Java & Python Medium Others
736 Parse Lisp Expression Java & Python Hard Others
738 Monotone Increasing Digits Java & Python Medium Others
740 Delete and Earn Java & Python Medium Others
741 Cherry Pickup Java & Python Hard Others
743 Network Delay Time Java & Python Medium Others
745 Prefix and Suffix Search Java & Python Hard Others
746 Min Cost Climbing Stairs Java & Python Easy Others
748 Shortest Completing Word Java & Python Easy Others
749 Contain Virus Java & Python Hard Others
753 Cracking the Safe Java & Python Hard Others
754 Reach a Number Java & Python Easy Others
756 Pyramid Transition Matrix Java & Python Medium Others
757 Set Intersection Size At Least Two Java & Python Hard Others
761 Special Binary String Java & Python Hard Others
762 Prime Number of Set Bits in Binary Representation Java & Python Easy Others
763 Partition Labels Java & Python Medium Others
764 Largest Plus Sign Java & Python Medium Others
765 Couples Holding Hands Java & Python Hard Others
766 Toeplitz Matrix Java & Python Easy Others
767 Reorganize String Java & Python Medium Others
768 Max Chunks To Make Sorted II Java & Python Hard Others
769 Max Chunks To Make Sorted Java & Python Medium Others
770 Basic Calculator IV Java & Python Hard Others
773 Sliding Puzzle Java & Python Hard Others
775 Global and Local Inversions Java & Python Medium Others
777 Swap Adjacent in LR String Java & Python Medium Others
778 Swim in Rising Water Java & Python Hard Others
780 Reaching Points Java & Python Hard Others
781 Rabbits in Forest Java & Python Medium Others
782 Transform to Chessboard Java & Python Hard Others
783 Minimum Distance Between BST Nodes Java & Python Easy Others
784 Letter Case Permutation Java & Python Easy Others
785 Is Graph Bipartite? Java & Python Medium Others
786 K-th Smallest Prime Fraction Java & Python Hard Others
787 Cheapest Flights Within K Stops Java & Python Medium Others
788 Rotated Digits Java & Python Easy Others
789 Escape The Ghosts Java & Python Medium Others
790 Domino and Tromino Tiling Java & Python Medium Others
791 Custom Sort String Java & Python Medium Others
792 Number of Matching Subsequences Java & Python Medium Others
793 Preimage Size of Factorial Zeroes Function Java & Python Hard Others
794 Valid Tic-Tac-Toe State Java & Python Medium Others
795 Number of Subarrays with Bounded Maximum Java & Python Medium Others
796 Rotate String Java & Python Easy Others
797 All Paths From Source to Target Java & Python Medium Others
798 Smallest Rotation with Highest Score Java & Python Hard Others
799 Champagne Tower Java & Python Medium Others
801 Minimum Swaps To Make Sequences Increasing Java & Python Medium Others
802 Find Eventual Safe States Java & Python Medium Others
803 Bricks Falling When Hit Java & Python Hard Others
804 Unique Morse Code Words Java & Python Easy Others
805 Split Array With Same Average Java & Python Hard Others
806 Number of Lines To Write String Java & Python Easy Others
807 Max Increase to Keep City Skyline Java & Python Medium Others
808 Soup Servings Java & Python Medium Others
809 Expressive Words Java & Python Medium Others
810 Chalkboard XOR Game Java & Python Hard Others
811 Subdomain Visit Count Java & Python Easy Others
812 Largest Triangle Area Java & Python Easy Others
813 Largest Sum of Averages Java & Python Medium Others
814 Binary Tree Pruning Java & Python Medium Others
815 Bus Routes Java & Python Hard Others
816 Ambiguous Coordinates Java & Python Medium Others
817 Linked List Components Java & Python Medium Others
818 Race Car Java & Python Hard Others
819 Most Common Word Java & Python Easy Others
820 Short Encoding of Words Java & Python Medium Others
821 Shortest Distance to a Character Java & Python Easy Others
822 Card Flipping Game Java & Python Medium Others
823 Binary Trees With Factors Java & Python Medium Others
824 Goat Latin Java & Python Easy Others
825 Friends Of Appropriate Ages Java & Python Medium Others
826 Most Profit Assigning Work Java & Python Medium Others
827 Making A Large Island Java & Python Hard Others
828 Unique Letter String Java & Python Hard Others
829 Consecutive Numbers Sum Java & Python Hard Others
830 Positions of Large Groups Java & Python Easy Others
831 Masking Personal Information Java & Python Medium Others
832 Flipping an Image Java & Python Easy Others
833 Find And Replace in String Java & Python Medium Others
834 Sum of Distances in Tree Java & Python Hard Others
835 Image Overlap Java & Python Medium Others
836 Rectangle Overlap Java & Python Easy Others
837 New 21 Game Java & Python Medium Others
838 Push Dominoes Java & Python Medium Others
839 Similar String Groups Java & Python Hard Others
840 Magic Squares In Grid Java & Python Easy Others
842 Split Array into Fibonacci Sequence Java & Python Medium Others
843 Guess the Word Java & Python Hard Others
844 Backspace String Compare Java & Python Easy Others
845 Longest Mountain in Array Java & Python Medium Others
846 Hand of Straights Java & Python Medium Others
847 Shortest Path Visiting All Nodes Java & Python Hard Others
848 Shifting Letters Java & Python Medium Others
849 Maximize Distance to Closest Person Java & Python Easy Others
850 Rectangle Area II Java & Python Hard Others
851 Loud and Rich Java & Python Medium Others
852 Peak Index in a Mountain Array Java & Python Easy Others
853 Car Fleet Java & Python Medium Others
854 K-Similar Strings Java & Python Hard Others
855 Exam Room Java & Python Medium Others
856 Score of Parentheses Java & Python Medium Others
857 Minimum Cost to Hire K Workers Java & Python Hard Others
858 Mirror Reflection Java & Python Medium Others
859 Buddy Strings Java & Python Easy Others
860 Lemonade Change Java & Python Easy Others
861 Score After Flipping Matrix Java & Python Medium Others
862 Shortest Subarray with Sum at Least K Java & Python Hard Others
863 All Nodes Distance K in Binary Tree Java & Python Medium Others
864 Shortest Path to Get All Keys Java & Python Hard Others
865 Smallest Subtree with all the Deepest Nodes Java & Python Medium Others
866 Prime Palindrome Java & Python Medium Others
867 Transpose Matrix Java & Python Easy Others
868 Binary Gap Java & Python Easy Others
869 Reordered Power of 2 Java & Python Medium Others
870 Advantage Shuffle Java & Python Medium Others
871 Minimum Number of Refueling Stops Java & Python Hard Others
872 Leaf-Similar Trees Java & Python Easy Others
873 Length of Longest Fibonacci Subsequence Java & Python Medium Others
874 Walking Robot Simulation Java & Python Easy Others
875 Koko Eating Bananas Java & Python Medium Others
876 Middle of the Linked List Java & Python Easy Others
877 Stone Game Java & Python Medium Others
878 Nth Magical Number Java & Python Hard Others
879 Profitable Schemes Java & Python Hard Others
880 Decoded String at Index Java & Python Medium Others
881 Boats to Save People Java & Python Medium Others
882 Reachable Nodes In Subdivided Graph Java & Python Hard Others
883 Projection Area of 3D Shapes Java & Python Easy Others
884 Uncommon Words from Two Sentences Java & Python Easy Others
885 Spiral Matrix III Java & Python Medium Others
886 Possible Bipartition Java & Python Medium Others
887 Super Egg Drop Java & Python Hard Others
888 Fair Candy Swap Java & Python Easy Others
889 Construct Binary Tree from Preorder and Postorder Traversal Java & Python Medium Others
890 Find and Replace Pattern Java & Python Medium Others
891 Sum of Subsequence Widths Java & Python Hard Others
892 Surface Area of 3D Shapes Java & Python Easy Others
893 Groups of Special-Equivalent Strings Java & Python Easy Others
894 All Possible Full Binary Trees Java & Python Medium Others
895 Maximum Frequency Stack Java & Python Hard Others
896 Monotonic Array Java & Python Easy Others
897 Increasing Order Search Tree Java & Python Easy Others
898 Bitwise ORs of Subarrays Java & Python Medium Others
899 Orderly Queue Java & Python Hard Others
900 RLE Iterator Java & Python Medium Others
901 Online Stock Span Java & Python Medium Others
902 Numbers At Most N Given Digit Set Java & Python Hard Others
903 Valid Permutations for DI Sequence Java & Python Hard Others
904 Fruit Into Baskets Java & Python Medium Others
905 Sort Array By Parity Java & Python Easy Others
906 Super Palindromes Java & Python Hard Others
907 Sum of Subarray Minimums Java & Python Medium Others
908 Smallest Range I Java & Python Easy Others
909 Snakes and Ladders Java & Python Medium Others
910 Smallest Range II Java & Python Medium Others
911 Online Election Java & Python Medium Others
913 Cat and Mouse Java & Python Hard Others
914 X of a Kind in a Deck of Cards Java & Python Easy Others
915 Partition Array into Disjoint Intervals Java & Python Medium Others

Shell

# Title Solutions Difficulty Tag
192 Word Frequency bash Medium Shell
193 Valid Phone Numbers bash Easy Shell
194 Transpose File bash Medium Shell
195 Tenth Line bash Easy Shell

Database

# Title Solutions Difficulty Tag
175 Combine Two Tables MySQL Easy Database
176 Second Highest Salary MySQL Easy Database
177 Nth Highest Salary MySQL Medium Database
178 Rank Scores MySQL Medium Database
180 Consecutive Numbers MySQL Medium Database
181 Employees Earning More Than Their Managers MySQL Easy Database
182 Duplicate Emails MySQL Easy Database
183 Customers Who Never Order MySQL Easy Database
184 Department Highest Salary MySQL Medium Database
185 Department Top Three Salaries MySQL Hard Database
196 Delete Duplicate Emails MySQL Easy Database
197 Rising Temperature MySQL Easy Database
262 Trips and Users MySQL Hard Database
595 Big Countries MySQL Easy Database
596 Classes More Than 5 Students MySQL Easy Database
601 Human Traffic of Stadium MySQL Hard Database
620 Not Boring Movies MySQL Easy Database
626 Exchange Seats MySQL Medium Database
627 Swap Salary MySQL Easy Database

Sort Algorithm

# Title Solutions Difficulty Tag
Sort 1 Bubble Sort Java & Python Easy Sort Algorithm
Sort 2 Insert Sort Java & Python Easy Sort Algorithm
Sort 3 Select Sort Java & Python Easy Sort Algorithm
Sort 4 Quick Sort Java & Python Easy Sort Algorithm
Sort 5 Merge Sort Java & Python Medium Sort Algorithm
Sort 6 Heap Sort Java & Python Medium Sort Algorithm
Sort 7 Bucket Sort Java & Python Easy Sort Algorithm

Search Algorithm

# Title Solutions Difficulty Tag
Search 1 Binary Search Java & Python Easy Search Algorithm
Search 2 Interpolation Search Java & Python Easy Search Algorithmx
Search 3 Order Search Java & Python Easy Search Algorithm

Interview

Top Interview Questions

Easy Collection

# Title Solutions Difficulty Tag
1 Two Sum Java & Python Easy Array
7 Reverse Integer Java & Python Easy Strings
8 String to Integer (atoi) Java & Python Medium Strings
13 Roman to Integer Java & Python Easy Math
14 Longest Common Prefix Java & Python Easy Strings
19 Remove Nth Node From End of List Java & Python Medium Linked List
20 Valid Parentheses Java & Python Easy Others
21 Merge Two Sorted Lists Java & Python Easy Linked List
26 Remove Duplicates from Sorted Array Java & Python Easy Array
28 Implement strStr() Java & Python Easy Strings
36 Valid Sudoku Java & Python Medium Array
38 Count and Say Java & Python Easy Strings
48 Rotate Image Java & Python Medium Array
53 Maximum Subarray Java & Python Easy Dynamic Programming
66 Plus One Java & Python Easy Array
70 Climbing Stairs Java & Python Easy Dynamic Programming
88 Merge Sorted Array Java & Python Easy Sorting and Searching
98 Validate Binary Search Tree Java & Python Medium Trees
101 Symmetric Tree Java & Python Easy Trees
102 Binary Tree Level Order Traversal Java & Python Medium Trees
104 Maximum Depth of Binary Tree Java & Python Easy Trees
108 Convert Sorted Array to Binary Search Tree Java & Python Easy Trees
118 Pascal’s Triangle Java & Python Easy Others
121 Best Time to Buy and Sell Stock Java & Python Easy Dynamic Programming
122 Remove Duplicates from Sorted Array Java & Python Easy Array
125 Valid Palindrome Java & Python Easy Strings
136 Single Number Java & Python Easy Array
141 Linked List Cycle Java & Python Easy Linked List
155 Min Stack Java & Python Easy Design
189 Rotate Array Java & Python Easy Array
190 Reverse Bits Java & Python Easy Others
191 Number of 1 Bits Java & Python Easy Others
198 House Robber Java & Python Easy Dynamic Programming
204 Count Primes Java & Python Easy Math
206 Reverse Linked List Java & Python Easy Linked List
217 Contains Duplicate Java & Python Easy Array
234 Palindrome Linked List Java & Python Easy Linked List
237 Delete Node in a Linked List Java & Python Easy Linked List
242 Valid Anagram Java & Python Easy Strings
268 Missing Number Java & Python Easy Others
278 First Bad Version Java & Python Easy Sorting and Searching
283 Move Zeroes Java & Python Easy Array
326 Power of Three Java & Python Easy Math
344 Reverse String Java & Python Easy Strings
350 Intersection of Two Arrays II Java & Python Easy Array
384 Shuffle an Array Java & Python Medium Design
387 First Unique Character in a String Java & Python Easy Strings
412 Fizz Buzz Java & Python Easy Math
461 Hamming Distance Java & Python Easy Others

Medium Collection

# Title Solutions Difficulty Tag
2 Add Two Numbers Java & Python Medium Linked List
3 Longest Substring Without Repeating Characters Java & Python Medium Array and Strings
5 Longest Palindromic Substring Java & Python Medium Array and Strings
15 3Sum Java & Python Medium Array and Strings
17 Letter Combinations of a Phone Number Java & Python Medium Backtracking
22 Generate Parentheses Java & Python Medium Backtracking
29 Divide Two Integers Java & Python Medium Math
33 Search in Rotated Sorted Array Java & Python Medium Sorting and Searching
34 Find First and Last Position of Element in Sorted Array Java & Python Medium Sorting and Searching
46 Permutations Java & Python Medium Backtracking
49 Group Anagrams Java & Python Medium Array and Strings
50 Pow(x, n) Java & Python Medium Math
55 Jump Game Java & Python Medium Dynamic Programming
56 Merge Intervals Java & Python Medium Sorting and Searching
62 Unique Paths Java & Python Medium Dynamic Programming
69 Sqrt(x) Java & Python Easy Math
73 Set Matrix Zeroes Java & Python Medium Array and Strings
75 Sort Colors Java & Python Medium Sorting and Searching
78 Subsets Java & Python Medium Backtracking
79 Word Search Java & Python Medium Backtracking
94 Binary Tree Inorder Traversal Java & Python Medium Trees and Graphs
103 Binary Tree Zigzag Level Order Traversal Java & Python Medium Trees and Graphs
105 Construct Binary Tree from Preorder and Inorder Traversal Java & Python Medium Trees and Graphs
116 Populating Next Right Pointers in Each Node Java & Python Medium Trees and Graphs
150 Evaluate Reverse Polish Notation Java & Python Medium Others
160 Intersection of Two Linked Lists Java & Python Easy Linked List
162 Find Peak Element Java & Python Medium Sorting and Searching
166 Fraction to Recurring Decimal Java & Python Medium Math
169 Majority Element Java & Python Easy Others
171 Excel Sheet Column Number Java & Python Easy Math
172 Factorial Trailing Zeroes Java & Python Easy Math
200 Number of Islands Java & Python Medium Trees and Graphs
202 Happy Number Java & Python Easy Math
215 Kth Largest Element in an Array Java & Python Medium Sorting and Searching
230 Kth Smallest Element in a BST Java & Python Medium Trees and Graphs
240 Search a 2D Matrix II Java & Python Medium Sorting and Searching
297 Serialize and Deserialize Binary Tree Java & Python Medium Design
300 Longest Increasing Subsequence Java & Python Medium Dynamic Programming
322 Coin Change Java & Python Medium Dynamic Programming
328 Odd Even Linked List Java & Python Medium Linked List
334 Increasing Triplet Subsequence Java & Python Medium Array and Strings
347 Top K Frequent Elements Java & Python Medium Sorting and Searching
371 Sum of Two Integers Java & Python Easy Others
380 Insert Delete GetRandom O(1) Java & Python Medium Design
621 Task Scheduler Java & Python Medium Others

Hard Collection

# Title Solutions Difficulty Tag
4 Median of Two Sorted Arrays Java & Python Hard Sorting and Searching
10 Regular Expression Matching Java & Python Hard Backtracking
11 Container With Most Water Java & Python Medium Array and Strings
23 Merge k Sorted Lists Java & Python Hard Linked List
41 First Missing Positive Java & Python Hard Array and Strings
42 Trapping Rain Water Java & Python Hard Others
44 Wildcard Matching Java & Python Hard Backtracking
54 Spiral Matrix Java & Python Medium Array and Strings
76 Minimum Window Substring Java & Python Hard Array and Strings
84 Largest Rectangle in Histogram Java & Python Hard Others
91 Decode Ways Java & Python Medium Dynamic Programming
124 Binary Tree Maximum Path Sum Java & Python Hard Trees and Graphs
127 Word Ladder Java & Python Medium Trees and Graphs
128 Longest Consecutive Sequence Java & Python Hard Array and Strings
130 Surrounded Regions Java & Python Medium Trees and Graphs
131 Palindrome Partitioning Java & Python Medium Backtracking
135 Copy List with Random Pointer Java & Python Medium Linked List
139 Word Break Java & Python Medium Dynamic Programming
140 Word Break II Java & Python Hard Dynamic Programming
146 LRU Cache Java & Python Medium Design
148 Sort List Java & Python Medium Linked List
149 Max Points on a Line Java & Python Hard Math
152 Maximum Product Subarray Java & Python Medium Dynamic Programming
179 Largest Number Java & Python Medium Math
207 Course Schedule Java & Python Medium Trees and Graphs
208 Implement Trie (Prefix Tree) Java & Python Medium Design
210 Course Schedule II Java & Python Medium Trees and Graphs
212 Word Search II Java & Python Hard Backtracing
218 The Skyline Problem Java & Python Hard Others
227 Basic Calculator II Java & Python Medium Array and Strings
236 Lowest Common Ancestor of a Binary Tree Java & Python Medium Trees and Graphs
238 Product of Array Except Self Java & Python Medium Array and Strings
239 Sliding Window Maximum Java & Python Hard Array and Strings
279 Perfect Squares Java & Python Medium Dynamic Programming
287 Find the Duplicate Number Java & Python Medium Array and Strings
289 Game of Life Java & Python Medium Array and Strings
295 Find Median from Data Stream Java & Python Hard Design
301 Remove Invalid Parentheses Java & Python Hard Backtracking
309 Best Time to Buy and Sell Stock with Cooldown Java & Python Medium Dynamic Programming
312 Burst Balloons Java & Python Hard Dynamic Programming
315 Count of Smaller Numbers After Self Java & Python Hard Trees and Graphs
324 Wiggle Sort II Java & Python Medium Sorting and Searching
329 Longest Increasing Path in a Matrix Java & Python Hard Trees and Graphs
341 Flatten Nested List Iterator Java & Python Medium Design
378 Kth Smallest Element in a Sorted Matrix Java & Python Medium Sorting and Searching
406 Queue Reconstruction by Height Java & Python Medium Others
454 4Sum II Java & Python Medium Array and Strings
547 Friend Circles Java & Python Medium Trees and Graphs