myleetcode

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
  • Queue & Stack
  • Linked List
  • Hash Table
  • Binary Search
  • Binary Tree
  • Binary Search Tree
  • N-ary Tree
  • Trie (Prefix Tree)
  • Decision Tree
  • Recursion I
  • Recursion II
  • Concurrency
  • Others
  • Shell
  • Database
  • Sort Algorithm
  • Search Algorithm
• Interview
  • Top Interview Questions
    • Easy Collection
    • Medium Collection
    • Hard Collection

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 & Go	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

Binary Search

#	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 & Go	Easy	Array
7	Reverse Integer	Java & Go	Easy	Strings
8	String to Integer (atoi)	Java & Python	Medium	Strings
13	Roman to Integer	Java & Python	Easy	Math
14	Longest Common Prefix	Java & Go	Easy	Strings
19	Remove Nth Node From End of List	Java & Go	Medium	Linked List
20	Valid Parentheses	Java & Python	Easy	Others
21	Merge Two Sorted Lists	Java & Go	Easy	Linked List
26	Remove Duplicates from Sorted Array	Java & Go	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 & Go	Medium	Array
53	Maximum Subarray	Java & Python	Easy	Dynamic Programming
66	Plus One	Java & Go	Easy	Array
70	Climbing Stairs	Java & Python	Easy	Dynamic Programming
88	Merge Sorted Array	Java & Go	Easy	Sorting and Searching
98	Validate Binary Search Tree	Java & Go	Medium	Trees
101	Symmetric Tree	Java & Go	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 & Go	Easy	Others
121	Best Time to Buy and Sell Stock	Java & Go	Easy	Dynamic Programming
122	Best Time to Buy and Sell Stock II	Java & Go	Easy	Array
125	Valid Palindrome	Java & Go	Easy	Strings
136	Single Number	Java & Go	Easy	Array
141	Linked List Cycle	Java & Go	Easy	Linked List
155	Min Stack	Java & Python	Easy	Design
189	Rotate Array	Java & Go	Easy	Array
190	Reverse Bits	Java & Python	Easy	Others
191	Number of 1 Bits	Java & Go	Easy	Others
198	House Robber	Java & Python	Easy	Dynamic Programming
204	Count Primes	Java & Go	Easy	Math
206	Reverse Linked List	Java & Go	Easy	Linked List
217	Contains Duplicate	Java & Go	Easy	Array
234	Palindrome Linked List	Java & Go	Easy	Linked List
237	Delete Node in a Linked List	Java & Go	Easy	Linked List
242	Valid Anagram	Java & Python	Easy	Strings
268	Missing Number	Java & Go	Easy	Others
278	First Bad Version	Java & Python	Easy	Sorting and Searching
283	Move Zeroes	Java & Go	Easy	Array
326	Power of Three	Java & Go	Easy	Math
344	Reverse String	Java & Go	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 & Go	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

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