Array

#	Title	Difficulty
565	Array Nesting	Medium
561	Array Partition I	Easy
605	Can Place Flowers	Easy
11	Container With Most Water	Medium
442	Find All Duplicates in an Array	Medium
448	Find All Numbers Disappeared in an Array	Easy
532	K-diff Pairs in an Array	Easy
500	Keyboard Row	Easy
485	Max Consecutive Ones	Easy
643	Maximum Average Subarray I	Easy
624	Maximum Distance in Arrays	Easy
88	Merge Sorted Array	Easy
283	Move Zeroes	Easy
238	Product of Array Except Self	Medium
26	Remove Duplicates from Sorted Array	Easy
80	Remove Duplicates from Sorted Array II	Medium
27	Remove Element	Easy
566	Reshape the Matrix	Easy
189	Rotate Array	Easy
48	Rotate Image	Medium
581	Shortest Unsorted Continuous Subarray	Easy
228	Summary Ranges	Medium
495	Teemo Attacking	Medium
414	Third Maximum Number	Easy
31	Next Permutation	Medium
611	Valid Triangle Number	Medium
15	3Sum	Medium
73	Set Matrix Zeroes	Medium
239	Sliding Window Maximum	Hard
665	Non-decreasing Array	Easy
674	Longest Continuous Increasing Subsequence	Easy
661	Image Smoother	Easy
697	Degree of an Array	Easy
724	[Find Pivot Index](https://github.com/FFIB/leetcode/blob/master/leetcode/Array/Fin
ivotIndex.swift)	Medium
717	1-bit and 2-bit Characters	Medium
713	Subarray Product Less Than K	Medium
118	Pascal's Triangle	Easy
119	Pascal's Triangle II	Easy
16	3Sum Closest	Medium
747	Largest Number At Least Twice of Others	Easy
769	Max Chunks To Make Sorted	Medium
768	Max Chunks To Make Sorted II	Hard
766	Toeplitz Matrix	Easy
795	Number of Subarrays with Bounded Maximum	Medium
822	Card Flipping Game	Medium
832	Flipping an Image	Easy
806	Number of Lines To Write String	Easy

String

#	Title	Difficulty
165	Compare Version Numbers	Medium
520	Detect Capital	Easy
28	Implement strStr()	Easy
58	Length of Last Word	Easy
521	Longest Uncommon Subsequence I	Easy
434	Number of Segments in a String	Easy
567	Permutation in String	Medium
383	Ransom Note	Easy
459	Repeated Substring Pattern	Easy
345	Reverse Vowels of a String	Easy
557	Reverse Words in a String III	Easy
551	Student Attendance Record I	Easy
125	Valid Palindrome	Easy
6	ZigZag Conversion	Medium
468	Validate IP Address	Medium
657	Judge Route Circle	Easy
680	Valid Palindrome II	Easy
678	Valid Parenthesis String	Medium
670	Maximum Swap	Medium
443	String Compression	Easy
14	Longest Common Prefix	Easy
696	Count Binary Substrings	Easy
38	Count and Say	Easy
539	Minimum Time Difference	Medium
5	Longest Palindromic Substring	Medium
556	Next Greater Element III	Medium
522	Longest Uncommon Subsequence II	Medium
763	Partition Labels	Medium
241	Different Ways to Add Parentheses	Medium
809	Expressive Words	Medium
791	Custom Sort String	Medium
804	Unique Morse Code Words	Easy
821	Shortest Distance to a Character	Easy
831	Masking Personal Information	Easy
424	Longest Repeating Character Replacement	Medium
819	Most Common Word	Easy
833	Find And Replace in String	Medium
824	Goat Latin	Easy
820	Short Encoding of Words	Medium
816	Ambiguous Coordinates	Medium
796	Rotate String	Easy

List

#	Title	Difficulty
2	Add Two Numbers	Medium
445	Add Two Numbers II	Medium
21	Merge Two Sorted Lists	Easy
328	Odd Even Linked List	Medium
234	Palindrome Linked List	Easy
83	Remove Duplicates from Sorted List	Easy
203	Remove Linked List Elements	Easy
19	Remove Nth Node From End of List	Medium
143	Reorder List	Medium
206	Reverse Linked List	Easy
61	Rotate List	Medium
24	Swap Nodes in Pairs	Medium
86	Partition List	Medium
82	Remove Duplicates from Sorted List II	Medium
725	Split Linked List in Parts	Medium
817	Linked List Components	Medium

Tree

#	Title	Difficulty
563	Binary Tree Tilt	Easy
538	Convert BST to Greater Tree	Easy
543	Diameter of Binary Tree	Easy
501	Find Mode in Binary Search Tree	Easy
226	Invert Binary Tree	Easy
617	Merge Two Binary Trees	Easy
437	Path Sum III	Easy
572	Subtree of Another Tree	Easy
530	Minimum Absolute Difference in BST	Easy
404	Sum of Left Leaves	Easy
654	Maximum Binary Tree	Medium
653	Two Sum IV - Input is a BST	Easy
637	Average of Levels in Binary Tree	Easy
669	Trim a Binary Search Tree	Easy
687	Longest Univalue Path	Easy
606	Construct String from Binary Tree	Easy
450	Delete Node in a BST	Medium
337	House Robber III	Medium
623	Add One Row to Tree	Medium
652	Find Duplicate Subtrees	Medium
655	Print Binary Tree	Medium
230	Kth Smallest Element in a BST	Medium
783	Minimum Distance Between BST Nodes	Easy
814	Binary Tree Pruning	Medium

Stack

#	Title	Difficulty
636	Exclusive Time of Functions	Medium
735	Asteroid Collision	Medium
682	Baseball Game	Easy
224	Basic Calculator	Hard
227	Basic CalculatorII	Medium
150	Evaluate Reverse Polish Notation	Medium
496	Next Greater Element I	Easy
503	Next Greater Element II	Medium
71	Simplify Path	Medium
42	Trapping Rain Water	Hard
20	Valid Parentheses	Easy
402	Remove K Digits	Medium
316	Remove Duplicate Letters	Hard
739	Daily Temperatures	Medium
385	Mini Parser	Medium
144	Binary Tree Preorder Traversal	Medium
94	Binary Tree Inorder Traversal	Medium
145	Binary Tree Postorder Traversal	Hard
199	Binary Tree Right Side View	Medium

Queue

#	Title	Difficulty
621	Task Scheduler	Medium
102	Binary Tree Level Order Traversal	Medium
107	Binary Tree Level Order Traversal II	Easy
103	Binary Tree Zigzag Level Order Traversal	Medium
662	Maximum Width of Binary Tree	Medium

Math

#	Title	Difficulty
65	Valid Number	Hard
263	Ugly Number	Easy
258	Add Digits	Easy
319	Bulb Switcher	Medium
168	Excel Sheet Column Title	Easy
172	Factorial Trailing Zeroes	Easy
12	Integer to Roman	Medium
553	Optimal Division	Medium
9	Palindrome Number	Easy
507	Perfect Number	Easy
400	Nth Digit	Easy
326	Power of Three	Easy
7	Reverse Integer	Easy
54	Spiral Matrix	Medium
59	Spiral Matrix II	Medium
633	Sum of Square Numbers	Easy
292	Nim Game	Easy
204	Count Primes	Easy
368	Largest Divisible Subset	Medium
223	Rectangle Area	Medium
372	Super Pow	Medium
593	Valid Square	Medium
667	Beautiful Arrangement II	Medium
640	Solve the Equation	Medium
672	Bulb Switcher II	Medium
728	Self Dividing Numbers	Easy
396	Rotate Function	Medium
628	Maximum Product of Three Numbers	Easy
453	Minimum Moves to Equal Array Elements	Easy
462	Minimum Moves to Equal Array Elements II	Medium
66	Plus One	Easy
598	Range Addition II	Easy
67	Add Binary	Easy
415	Add Strings	Easy
171	Excel Sheet Column Number	Easy
423	Reconstruct Original Digits from English	Medium
13	Roman to Integer	Easy
8	String to Integer (atoi)	Medium
592	Fraction Addition and Subtraction	Medium
754	Reach a Number	Medium
43	Multiply Strings	Medium
313	Super Ugly Number	Medium
812	Largest Triangle Area	Easy
829	Consecutive Numbers Sum	Medium
830	Positions of Large Groups	Medium
789	Escape The Ghosts	Medium

Sort

#	Title	Difficulty
75	Sort Colors	Medium
324	Wiggle Sort II	Medium
274	H-Index	Medium
57	Insert Interval	Hard
147	Insertion Sort List	Medium
215	Kth Largest Element in an Array	Medium
524	Longest Word in Dictionary through Deleting	Medium
56	Merge Intervals	Medium
825	Friends Of Appropriate Ages	Medium
826	Most Profit Assigning Work	Medium

DP

#	Title	Difficulty
62	Unique Paths	Medium
63	Unique Paths II	Medium
91	Decode Ways	Medium
64	Minimum Path Sum	Medium
494	Target Sum	Medium
688	Knight Probability in Chessboard	Medium
139	Word Break	Medium
140	Word BreakII	Medium
96	Unique Binary Search Trees	Medium
95	Unique Binary Search Tree II	Medium
300	Longest Increasing Subsequence	Medium
467	Unique Substrings in Wraparound String	Medium
650	2 Keys Keyboard	Medium
123	Best Time to Buy and Sell Stock III	Hard
312	Burst Balloons	Hard
413	Arithmetic Slices	Medium
121	Best Time to Buy and Sell Stock	Easy
70	Climbing Stairs	Easy
377	Combination Sum IV	Medium
523	Continuous Subarray Sum	Medium
357	Count Numbers with Unique Digits	Medium
375	Guess Number Higher or Lower II	Medium
198	House Robber	Easy
213	House Robber II	Medium
343	Integer Break	Medium
629	K Inverse Pairs Array	Hard
516	Longest Palindromic Subsequence	Medium
221	Maximal Square	Medium
646	Maximum Length of Pair Chain	Medium
152	Maximum Product Subarray	Medium
647	Palindromic Substrings	Medium
416	Partition Equal Subset Sum	Medium
120	Triangle	Medium
264	Ugly Number II	Medium
740	Delete and Earn	Medium
718	Maximum Length of Repeated Subarray	Medium
746	Min Cost Climbing Stairs	Easy
583	Delete Operation for Two Strings	Medium
712	Minimum ASCII Delete Sum for Two Strings	Medium
698	Partition to K Equal Sum Subsets	Medium
823	Binary Trees With Factors	Medium
813	Largest Sum of Averages	Medium
801	Minimum Swaps To Make Sequences Increasing	Medium

BFS

#	Title	Difficulty
130	Surrounded Regions	Medium
752	Open the Lock	Medium

Backtracking

#	Title	Difficulty
526	Beautiful Arrangement	Medium
77	Combinations	Medium
39	Combination Sum	Medium
40	Combination Sum II	Medium
216	Combination Sum III	Medium
22	Generate Parentheses	Medium
17	Letter Combinations of a Phone Number	Medium
46	Permutations	Medium
47	Permutations II	Medium
78	Subsets	Medium
90	Subsets II	Medium
79	Word Search	Medium

Binary Search

#	Title	Difficulty
441	Arranging Coins	Easy
153	Find Minimum in Rotated Sorted Array	Medium
154	Find Minimum in Rotated Sorted Array II	Hard
33	Search in Rotated Sorted Array	Medium
81	Search in Rotated Sorted Array II	Medium
162	Find Peak Element	Medium
287	Find the Duplicate Number	Medium
475	Heaters	Easy
378	Kth Smallest Element in a Sorted Matrix	Medium
4	Median of Two Sorted Arrays	Hard
290	Minimum Size Subarray Sum	Medium
50	Pow(x, n)	Medium
74	Search a 2D Matrix	Medium
35	Search Insert Position	Easy
34	Search for a Range	Medium
167	Two Sum II - Input array is sorted	Easy
367	Valid Perfect Square	Easy
658	Find K Closest Elements	Medium
744	Find Smallest Letter Greater Than Target	Medium

Bit Manipulation

#	Title	Difficulty
693	Binary Number with Alternating Bits	Easy
405	Convert a Number to Hexadecimal	Easy
338	Counting Bits	Medium
461	Hamming Distance	Easy
397	Integer Replacement	Medium
268	Missing Number	Easy
476	Number Complement	Easy
231	Power of Two	Easy
342	Power of Four	Easy
136	Single Number	Easy
137	Single Number II	Medium
260	Single Number III	Medium
371	Sum of Two Integers	Easy
477 Total Hamming Distance	Medium

DFS

#	Title	Difficulty
110	Balanced Binary Tree	Easy
257	Binary Tree Paths	Easy
108	Convert Sorted Array to Binary Search Tree	Easy
394	Decode String	Medium
513	Find Bottom Left Tree Value	Medium
515	Find Largest Value in Each Tree Row	Medium
695	Max Area of Island	Easy
104	Maximum Depth of Binary Tree	Easy
111	Minimum Depth of Binary Tree	Easy
112	Path Sum	Easy
113	Path Sum II	Medium
100	Same Tree	Easy
101	Symmetric Tree	Easy
733	Flood Fill	Easy
129	Sum Root to Leaf Numbers	Medium
105	Construct Binary Tree from Preorder and Inorder Traversal	Medium
106	Construct Binary Tree from Inorder and Postorder Traversal	Medium
114	Flatten Binary Tree to Linked List	Medium
98	Validate Binary Search Tree	Medium
547	Friend Circles	Medium
638	Shopping Offers	Medium
464	Can I Win	Medium
797	All Paths From Source to Target	Medium

Divide and Conquer

#	Title	Difficulty
53	Maximum Subarray	Easy
240	Search a 2D Matrix II	Medium

Greedy

#	Title	Difficulty
455	Assign Cookies	Easy
122	Best Time to Buy and Sell Stock II	Easy
392	is Subsequence	Medium
55	Jump Game	Medium
452	Minimum Number of Arrows to Burst Balloons	Medium
435	Non-overlapping Intervals	Medium
406	Queue Reconstruction by Height	Medium
376	Wiggle Subsequence	Medium
738	Monotone Increasing Digits	Medium
649	Dota2 Senate	Medium
659	Split Array into Consecutive Subsequences	Medium

Map

#	Title	Difficulty
560	Subarray Sum Equals K	Medium

Hash Table

#	Title	Difficulty
554	Brick Wall	Medium
299	Bulls and Cows	Medium
217	Contains Duplicate	Easy
219	Contains Duplicate II	Easy
575	Distribute Candies	Easy
438	Find All Anagrams in a String	Easy
609	Find Duplicate File in System	Medium
18	4Sum	Medium
166	Fraction to Recurring Decimal	Medium
49	Group Anagrams	Medium
202	Happy Number	Easy
349	Intersection of Two Arrays	Easy
350	Intersection of Two Arrays II	Easy
463	Island Perimeter	Easy
594	Longest Harmonious Subsequence	Easy
409	Longest Palindrome	Easy
3	Longest Substring Without Repeating Characters	Medium
169	Majority Element	Easy
229	Majority Element II	Medium
599	Minimum Index Sum of Two Lists	Easy
76	Minimum Window Substring	Hard
508	Most Frequent Subtree Sum	Medium
506	Relative Ranks	Easy
648	Replace Words	Medium
645	Set Mismatch	Easy
632	Smallest Range	Hard
451	Sort Characters By Frequency	Medium
30	Substring with Concatenation of All Words	Hard
347	Top K Frequent Elements	Medium
692	Top K Frequent Words	Medium
1	Two Sum	Easy
242	Valid Anagram	Easy
290	Word Pattern	Easy
454	4Sum II	Medium
336	Palindrome Pairs	Hard
720	Longest Word in Dictionary	Easy
748	Shortest Completing Word	Medium
525	Contiguous Array	Medium
187	Repeated DNA Sequences	Medium
781	Rabbits in Forest	Medium
811	Subdomain Visit Count	Easy

Unknown

#	Title	Difficulty
504	Base 7	Easy
419	Battleships in a Board	Medium
492	Construct the Rectangle	Easy
498	Diagonal Traverse	Medium
390	Elimination Game	Medium
387	First Unique Character in a String	Easy
412	Fizz Buzz	Easy
334	Increasing Triplet Subsequence	Medium
479	Largest Palindrome Product	Easy
482	License Key Formatting	Medium
388	Longest Absolute File Path	Medium
481	Magical String	Medium
540	Single Element in a Sorted Array	Medium