All Problems

519 problems · search by name, LC#, or tag · filter by difficulty & category

519 matches

#	Title	Difficulty	Category	Tags
1	Two Sum	Easy	Arrays	arrayhash-table
2	Add Two Numbers	Medium	Linked List	linked-listmathrecursion
3	Longest Substring Without Repeating Characters	Medium	Strings	hash-tablestringsliding-window
4	Median of Two Sorted Arrays	Hard	Sorting	arraybinary-searchdivide-and-conquer
5	Longest Palindromic Substring	Medium	Strings	two-pointersstringdynamic-programming
6	Zigzag Conversion	Medium	Strings	string
7	Reverse Integer	Medium	Math	math
8	String to Integer (atoi)	Medium	Strings	string
9	Palindrome Number	Easy	Strings	math
10	Regular Expression Matching	Hard	Dynamic Programming	stringdynamic-programmingrecursion
11	Container With Most Water	Medium	Arrays	arraytwo-pointersgreedy
12	Integer to Roman	Medium	Math	hash-tablemathstring
13	Roman to Integer	Easy	Math	hash-tablemathstring
14	Longest Common Prefix	Easy	Strings	arraystringtrie
15	3Sum	Medium	Arrays	arraytwo-pointerssorting
16	3Sum Closest	Medium	Arrays	arraytwo-pointerssorting
17	Letter Combinations of a Phone Number	Medium	Backtracking	hash-tablestringbacktracking
18	4Sum	Medium	Arrays	arraytwo-pointerssorting
19	Remove Nth Node From End of List	Medium	Linked List	linked-listtwo-pointers
20	Valid Parentheses	Easy	Strings	stringstack
21	Merge Two Sorted Lists	Easy	Linked List	linked-listrecursion
22	Generate Parentheses	Medium	Backtracking	stringdynamic-programmingbacktracking
23	Merge k Sorted Lists	Hard	Linked List	linked-listdivide-and-conquerheap-priority-queuemerge-sort
24	Swap Nodes in Pairs	Medium	Linked List	linked-listrecursion
25	Reverse Nodes in k-Group	Hard	Strings	linked-listrecursion
26	Remove Duplicates from Sorted Array	Easy	Arrays	arraytwo-pointers
27	Remove Element	Easy	LeetCode	arraytwo-pointers
30	Substring with Concatenation of All Words	Hard	Strings	hash-tablestringsliding-window
31	Next Permutation	Medium	Backtracking	arraytwo-pointerspermutation
32	Longest Valid Parentheses	Hard	Strings	stringdynamic-programmingstack
33	Search in Rotated Sorted Array	Medium	Arrays	arraybinary-search
34	Find First and Last Position of Element in Sorted Array	Medium	LeetCode	arraybinary-search
35	Search Insert Position	Easy	Arrays	arraybinary-search
36	Valid Sudoku	Medium	Matrix	arrayhash-tablematrix
37	Sudoku Solver	Hard	Matrix	arrayhash-tablebacktrackingmatrix
38	Count and Say	Medium	LeetCode	string
39	Combination Sum	Medium	Backtracking	arraybacktracking
40	Combination Sum II	Medium	Backtracking	arraybacktracking
41	First Missing Positive	Hard	LeetCode	arrayhash-table
42	Trapping Rain Water	Hard	Arrays	arraytwo-pointersdynamic-programmingstack
43	Multiply Strings	Medium	Strings	mathstringsimulation
44	Wildcard Matching	Hard	Dynamic Programming	stringdynamic-programminggreedyrecursion
45	Jump Game II	Medium	Greedy	arraydynamic-programminggreedy
46	Permutations	Medium	Backtracking	backtrackingrecursionarray
47	Permutations II	Medium	Backtracking	arraybacktrackingsorting
48	Rotate Image	Medium	Matrix	arraymathmatrix
49	Group Anagrams	Medium	Strings	arrayhash-tablestringsorting
50	Pow(x, n)	Medium	Math	mathrecursion
51	N-Queens	Hard	Backtracking	arraybacktracking
52	N-Queens II	Hard	Backtracking	backtracking
53	Maximum Subarray	Medium	Arrays	arraydynamic-programmingdivide-and-conquerkadanes-algorithm
53	Maximum Subarray	Medium	Arrays	arraydivide-and-conquerdynamic-programming
54	Spiral Matrix	Medium	Matrix	arraymatrixsimulation
55	Jump Game	Medium	Greedy	arraydynamic-programminggreedy
56	Merge Intervals	Medium	Sorting	arraysorting
57	Insert Interval	Medium	Sorting	array
58	Length of Last Word	Easy	Strings	string
59	Spiral Matrix II	Medium	Matrix	arraymatrixsimulation
60	Permutation Sequence	Hard	LeetCode	mathrecursion
61	Rotate List	Medium	Linked List	linked-listtwo-pointers
62	Unique Paths	Medium	Dynamic Programming	mathdynamic-programmingcombinatorics
63	Unique Paths II	Medium	Dynamic Programming	arraydynamic-programmingmatrix
64	Minimum Path Sum	Medium	Dynamic Programming	arraydynamic-programmingmatrix
65	Valid Number	Hard	Strings	string
66	Plus One	Easy	Arrays	arraymath
67	Add Binary	Easy	LeetCode	mathstringbit-manipulationsimulation
68	Text Justification	Hard	Strings	arraystringsimulation
69	Sqrt(x)	Easy	Math	mathbinary-search
70	Climbing Stairs	Easy	Dynamic Programming	mathdynamic-programmingmemoization
71	Simplify Path	Medium	Strings	stringstack
72	Edit Distance	Medium	Dynamic Programming	stringdynamic-programming
73	Set Matrix Zeroes	Medium	Matrix	arrayhash-tablematrix
74	Search a 2D Matrix	Medium	Matrix	arraybinary-searchmatrix
75	Sort Colors	Medium	Sorting	arraytwo-pointerssorting
76	Minimum Window Substring	Hard	Strings	hash-tablestringsliding-window
77	Combinations	Medium	Backtracking	backtracking
78	Subsets	Medium	Backtracking	arraybacktrackingbit-manipulation
79	Word Search	Medium	Backtracking	arraystringbacktrackingdepth-first-search
80	Remove Duplicates from Sorted Array II	Medium	Arrays	arraytwo-pointers
81	Search in Rotated Sorted Array II	Medium	Arrays	arraybinary-search
82	Remove Duplicates from Sorted List II	Medium	Arrays	linked-listtwo-pointers
83	Remove Duplicates from Sorted List	Easy	Arrays	linked-list
84	Largest Rectangle in Histogram	Hard	Math	arraystackmonotonic-stack
85	Maximal Rectangle	Hard	Dynamic Programming	arraydynamic-programmingstackmatrix
86	Partition List	Medium	Dynamic Programming	linked-listtwo-pointers
88	Merge Sorted Array	Easy	LeetCode	arraytwo-pointerssorting
89	Gray Code	Medium	LeetCode	mathbacktrackingbit-manipulation
90	Subsets II	Medium	Backtracking	arraybacktrackingbit-manipulation
91	Decode Ways	Medium	Dynamic Programming	stringdynamic-programming
92	Reverse Linked List II	Medium	Linked List	linked-list
93	Restore IP Addresses	Medium	Backtracking	stringbacktracking
94	Binary Tree Inorder Traversal	Easy	Trees	stacktreedepth-first-searchbinary-tree
95	Unique Binary Search Trees II	Medium	Trees	dynamic-programmingbacktrackingtreebinary-search-tree
96	Unique Binary Search Trees	Medium	Trees	mathdynamic-programmingtreebinary-search-tree
98	Validate Binary Search Tree	Medium	Trees	treedepth-first-searchbinary-search-treebinary-tree
100	Same Tree	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
101	Symmetric Tree	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
102	Binary Tree Level Order Traversal	Medium	Trees	treebfsqueue
103	Binary Tree Zigzag Level Order Traversal	Medium	Trees	treebreadth-first-searchbinary-tree
104	Maximum Depth of Binary Tree	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	Trees	arrayhash-tabledivide-and-conquertree
106	Construct Binary Tree from Inorder and Postorder Traversal	Medium	Trees	arrayhash-tabledivide-and-conquertree
107	Binary Tree Level Order Traversal II	Medium	Trees	treebreadth-first-searchbinary-tree
108	Convert Sorted Array to Binary Search Tree	Easy	Trees	arraydivide-and-conquertreebinary-search-tree
109	Convert Sorted List to Binary Search Tree	Medium	Trees	linked-listdivide-and-conquertreebinary-search-tree
110	Balanced Binary Tree	Easy	Trees	treedepth-first-searchbinary-tree
111	Minimum Depth of Binary Tree	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
112	Path Sum	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
113	Path Sum II	Medium	Trees	backtrackingtreedepth-first-searchbinary-tree
114	Flatten Binary Tree to Linked List	Medium	Trees	linked-liststacktreedepth-first-search
116	Populating Next Right Pointers in Each Node	Medium	Trees	linked-listtreedepth-first-searchbreadth-first-search
117	Populating Next Right Pointers in Each Node II	Medium	Trees	linked-listtreedepth-first-searchbreadth-first-search
118	Pascal's Triangle	Easy	Dynamic Programming	arraydynamic-programming
119	Pascal's Triangle II	Easy	Dynamic Programming	arraydynamic-programming
120	Triangle	Medium	Dynamic Programming	arraydynamic-programming
121	Best Time to Buy and Sell Stock	Easy	Dynamic Programming	arraydynamic-programming
122	Best Time to Buy and Sell Stock II	Medium	Dynamic Programming	arraydynamic-programminggreedy
123	Best Time to Buy and Sell Stock III	Hard	Dynamic Programming	arraydynamic-programming
125	Valid Palindrome	Easy	Strings	two-pointersstring
128	Longest Consecutive Sequence	Medium	LeetCode	arrayhash-tableunion-find
129	Sum Root to Leaf Numbers	Medium	Trees	treedepth-first-searchbinary-tree
133	Clone Graph	Medium	Graph	hash-tabledepth-first-searchbreadth-first-searchgraph
136	Single Number	Easy	Bit Manipulation	arraybit-manipulation
137	Single Number II	Medium	Bit Manipulation	arraybit-manipulation
138	Copy List with Random Pointer	Medium	Math	hash-tablelinked-list
139	Word Break	Medium	Dynamic Programming	dynamic-programmingstringtriememoization
140	Word Break II	Hard	Dynamic Programming	arrayhash-tablestringdynamic-programming
141	Linked List Cycle	Easy	Linked List	hash-tablelinked-listtwo-pointers
142	Linked List Cycle II	Medium	Linked List	hash-tablelinked-listtwo-pointers
143	Reorder List	Medium	Linked List	linked-listtwo-pointersstackrecursion
144	Binary Tree Preorder Traversal	Easy	Trees	stacktreedepth-first-searchbinary-tree
145	Binary Tree Postorder Traversal	Easy	Trees	stacktreedepth-first-searchbinary-tree
146	LRU Cache	Medium	Design	hash-tablelinked-listdesigndoubly-linked-list
147	Insertion Sort List	Medium	Linked List	linked-listsorting
148	Sort List	Medium	Linked List	linked-listtwo-pointersdivide-and-conquersorting
150	Evaluate Reverse Polish Notation	Medium	Strings	arraymathstack
151	Reverse Words in a String	Medium	Strings	two-pointersstring
152	Maximum Product Subarray	Medium	Arrays	arraydynamic-programming
153	Find Minimum in Rotated Sorted Array	Medium	Arrays	arraybinary-search
154	Find Minimum in Rotated Sorted Array II	Hard	Arrays	arraybinary-search
155	Min Stack	Medium	Design	stackdesign
160	Intersection of Two Linked Lists	Easy	Linked List	hash-tablelinked-listtwo-pointers
162	Find Peak Element	Medium	LeetCode	arraybinary-search
165	Compare Version Numbers	Medium	Strings	two-pointersstring
167	Two Sum II - Input Array Is Sorted	Medium	Arrays	arraytwo-pointersbinary-search
168	Excel Sheet Column Title	Easy	LeetCode	mathstring
169	Majority Element	Easy	Arrays	arrayhash-tabledivide-and-conquersorting
171	Excel Sheet Column Number	Easy	LeetCode	mathstring
173	Binary Search Tree Iterator	Medium	Trees	stacktreedesignbinary-search-tree
174	Dungeon Game	Hard	Dynamic Programming	arraydynamic-programmingmatrix
175	Combine Two Tables	Easy	SQL	database
176	Second Highest Salary	Medium	SQL	database
177	Nth Highest Salary	Medium	SQL	database
178	Rank Scores	Medium	SQL	database
179	Largest Number	Medium	Sorting	arraystringgreedysorting
180	Consecutive Numbers	Medium	SQL	database
181	Employees Earning More Than Their Managers	Easy	SQL	database
182	Duplicate Emails	Easy	SQL	database
183	Customers Who Never Order	Easy	SQL	database
184	Department Highest Salary	Medium	SQL	database
185	Department Top Three Salaries	Hard	SQL	database
189	Rotate Array	Medium	Arrays	arraymathtwo-pointers
190	Reverse Bits	Easy	Bit Manipulation	divide-and-conquerbit-manipulation
191	Number of 1 Bits	Easy	Bit Manipulation	divide-and-conquerbit-manipulation
192	Word Frequency	Medium	LeetCode	shell
193	Valid Phone Numbers	Easy	LeetCode	shell
196	Delete Duplicate Emails	Easy	SQL	database
197	Rising Temperature	Easy	SQL	database
198	House Robber	Medium	Dynamic Programming	arraydynamic-programming
199	Binary Tree Right Side View	Medium	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
200	Island Problems	Medium	Graph	graphdfsbfsmatrix
200	Number of Islands	Medium	Graph	graphdfsbfsmatrix
201	Bitwise AND of Numbers Range	Medium	Bit Manipulation	bit-manipulation
202	Happy Number	Easy	Math	hash-tablemathtwo-pointers
203	Remove Linked List Elements	Easy	Linked List	linked-listrecursion
204	Count Primes	Medium	Math	arraymathenumerationnumber-theory
205	Isomorphic Strings	Easy	Strings	hash-tablestring
206	Reverse Linked List	Easy	Linked List	linked-listrecursion
207	Course Schedule	Medium	Graph	depth-first-searchbreadth-first-searchgraphtopological-sort
208	Implement Trie (Prefix Tree)	Medium	Trie	hash-tablestringdesigntrie
209	Minimum Size Subarray Sum	Medium	Arrays	arraybinary-searchsliding-windowprefix-sum
210	Course Schedule II	Medium	Graph	depth-first-searchbreadth-first-searchgraphtopological-sort
213	House Robber II	Medium	Dynamic Programming	arraydynamic-programming
215	Kth Largest Element in an Array	Medium	Sorting	arraydivide-and-conquersortingheap-priority-queue
216	Combination Sum III	Medium	Backtracking	arraybacktracking
217	Contains Duplicate	Easy	Arrays	arrayhash-tablesorting
219	Contains Duplicate II	Easy	Arrays	arrayhash-tablesliding-window
221	Maximal Square	Medium	Dynamic Programming	arraydynamic-programmingmatrix
222	Count Complete Tree Nodes	Easy	Trees	binary-searchbit-manipulationtreebinary-tree
223	Rectangle Area	Medium	Math	mathgeometry
224	Basic Calculator	Hard	Stack	mathstringstackrecursion
225	Implement Stack using Queues	Easy	Design	stackdesignqueue
226	Invert Binary Tree	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
227	Basic Calculator II	Medium	Stack	mathstringstack
228	Summary Ranges	Easy	Arrays	array
229	Majority Element II	Medium	Arrays	arrayhash-tablesortingcounting
230	Kth Smallest Element in a BST	Medium	Trees	treedepth-first-searchbinary-search-treebinary-tree
231	Power of Two	Easy	Bit Manipulation	mathbit-manipulationrecursion
232	Implement Queue using Stacks	Easy	Design	stackdesignqueue
234	Palindrome Linked List	Easy	Linked List	linked-listtwo-pointersstackrecursion
235	Lowest Common Ancestor of a Binary Search Tree	Medium	Trees	treedepth-first-searchbinary-search-treebinary-tree
236	Lowest Common Ancestor of a Binary Tree	Medium	Trees	treedepth-first-searchbinary-tree
237	Delete Node in a Linked List	Medium	Linked List	linked-list
238	Product of Array Except Self	Medium	Arrays	arrayprefix-sum
239	Sliding Window Maximum	Hard	Arrays	arrayqueuesliding-windowheap-priority-queue
240	Search a 2D Matrix II	Medium	Matrix	arraybinary-searchdivide-and-conquermatrix
242	Valid Anagram	Easy	Strings	hash-tablestringsorting
257	Binary Tree Paths	Easy	Trees	stringbacktrackingtreedepth-first-search
258	Add Digits	Easy	Math	mathsimulationnumber-theory
263	Ugly Number	Easy	Math	math
268	Missing Number	Easy	Bit Manipulation	arrayhash-tablemathbinary-search
273	Integer to English Words	Hard	Strings	mathstringrecursion
274	H-Index	Medium	Sorting	arraysortingcounting-sort
275	H-Index II	Medium	Sorting	arraybinary-search
278	First Bad Version	Easy	LeetCode	binary-searchinteractive
279	Perfect Squares	Medium	Dynamic Programming	mathdynamic-programmingbreadth-first-search
283	Move Zeroes	Easy	Arrays	arraytwo-pointers
290	Word Pattern	Easy	LeetCode	hash-tablestring
295	Find Median from Data Stream	Hard	Sorting	two-pointersdesignsortingheap-priority-queue
297	Serialize and Deserialize Binary Tree	Hard	Trees	stringtreedepth-first-searchbreadth-first-search
303	Range Sum Query - Immutable	Easy	Design	arraydesignprefix-sum
304	Range Sum Query 2D - Immutable	Medium	Design	arraydesignmatrixprefix-sum
307	Range Sum Query - Mutable	Medium	Design	arraydivide-and-conquerdesignbinary-indexed-tree
312	Burst Balloons	Hard	Dynamic Programming	arraydynamic-programming
318	Maximum Product of Word Lengths	Medium	SQL	arraystringbit-manipulation
319	Bulb Switcher	Medium	Math	mathbrainteaser
322	Coin Change	Medium	Dynamic Programming	dynamic-programmingarraybfs
324	Wiggle Sort II	Medium	Sorting	arraydivide-and-conquergreedysorting
326	Power of Three	Easy	Bit Manipulation	mathrecursion
328	Odd Even Linked List	Medium	Linked List	linked-list
329	Longest Increasing Path in a Matrix	Hard	Matrix	arraydynamic-programmingdepth-first-searchbreadth-first-search
332	Reconstruct Itinerary	Hard	Graph	arraystringdepth-first-searchgraph
337	House Robber III	Medium	Dynamic Programming	dynamic-programmingtreedepth-first-searchbinary-tree
338	Counting Bits	Easy	Bit Manipulation	dynamic-programmingbit-manipulation
342	Power of Four	Easy	Bit Manipulation	mathbit-manipulationrecursion
344	Reverse String	Easy	Strings	two-pointersstring
345	Reverse Vowels of a String	Easy	Strings	two-pointersstring
347	Top K Frequent Elements	Medium	Sorting	arrayhash-tabledivide-and-conquersorting
349	Intersection of Two Arrays	Easy	Linked List	arrayhash-tabletwo-pointersbinary-search
350	Intersection of Two Arrays II	Easy	Linked List	arrayhash-tabletwo-pointersbinary-search
357	Count Numbers with Unique Digits	Medium	LeetCode	mathdynamic-programmingbacktracking
374	Guess Number Higher or Lower	Easy	LeetCode	binary-searchinteractive
383	Ransom Note	Easy	Strings	hash-tablestringcounting
384	Shuffle an Array	Medium	Math	arraymathdesignrandomized
387	First Unique Character in a String	Easy	Strings	hash-tablestringqueuecounting
394	Decode String	Medium	Strings	stringstackrecursion
395	Longest Substring with At Least K Repeating Characters	Medium	Strings	hash-tablestringdivide-and-conquersliding-window
402	Remove K Digits	Medium	Greedy	stringstackgreedymonotonic-stack
403	Frog Jump	Hard	Dynamic Programming	arraydynamic-programming
409	Longest Palindrome	Easy	Strings	hash-tablestringgreedy
412	Fizz Buzz	Easy	Math	mathstringsimulation
413	Arithmetic Slices	Medium	LeetCode	arraydynamic-programmingsliding-window
415	Add Strings	Easy	Strings	mathstringsimulation
416	Partition Equal Subset Sum	Medium	Dynamic Programming	arraydynamic-programming
419	Battleships in a Board	Medium	Matrix	arraydepth-first-searchmatrix
424	Longest Repeating Character Replacement	Medium	LeetCode	hash-tablestringsliding-window
442	Find All Duplicates in an Array	Medium	LeetCode	arrayhash-tablesorting
443	String Compression	Medium	Strings	two-pointersstring
445	Add Two Numbers II	Medium	Linked List	linked-listmathstack
448	Find All Numbers Disappeared in an Array	Easy	LeetCode	arrayhash-table
449	Serialize and Deserialize BST	Medium	Trees	stringtreedepth-first-searchbreadth-first-search
450	Delete Node in a BST	Medium	Trees	treebinary-search-treebinary-tree
451	Sort Characters By Frequency	Medium	Heap	hash-tablestringsortingheap-priority-queue
453	Minimum Moves to Equal Array Elements	Medium	LeetCode	arraymath
459	Repeated Substring Pattern	Easy	Strings	stringstring-matching
461	Hamming Distance	Easy	Bit Manipulation	bit-manipulation
462	Minimum Moves to Equal Array Elements II	Medium	LeetCode	arraymathsorting
463	Island Perimeter	Easy	Matrix	arraydepth-first-searchbreadth-first-searchmatrix
473	Matchsticks to Square	Medium	LeetCode	arraydynamic-programmingbacktrackingbit-manipulation
475	Heaters	Medium	LeetCode	arraytwo-pointersbinary-searchsorting
477	Total Hamming Distance	Medium	Bit Manipulation	arraymathbit-manipulation
480	Sliding Window Median	Hard	Sorting	arrayhash-tablesliding-windowheap-priority-queue
485	Max Consecutive Ones	Easy	LeetCode	array
494	Target Sum	Medium	Dynamic Programming	arraydynamic-programmingbacktracking
495	Teemo Attacking	Easy	Greedy	arraysimulation
496	Next Greater Element I	Easy	Stack	arrayhash-tablestackmonotonic-stack
498	Diagonal Traverse	Medium	Matrix	arraymatrixsimulation
500	Keyboard Row	Easy	Dynamic Programming	arrayhash-tablestring
503	Next Greater Element II	Medium	Stack	arraystackmonotonic-stack
506	Relative Ranks	Easy	LeetCode	arraysortingheap-priority-queue
513	Find Bottom Left Tree Value	Medium	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
515	Find Largest Value in Each Tree Row	Medium	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
516	Longest Palindromic Subsequence	Medium	Dynamic Programming	stringdynamic-programming
525	Contiguous Array	Medium	LeetCode	arrayhash-tableprefix-sum
530	Minimum Absolute Difference in BST	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-search-tree
532	K-diff Pairs in an Array	Medium	LeetCode	arrayhash-tabletwo-pointersbinary-search
535	Encode and Decode TinyURL	Medium	Design	hash-tablestringdesignhash-function
540	Single Element in a Sorted Array	Medium	LeetCode	arraybinary-search
541	Reverse String II	Easy	Strings	two-pointersstring
542	01 Matrix	Medium	Matrix	arraydynamic-programmingbreadth-first-searchmatrix
543	Diameter of Binary Tree	Easy	Trees	treedepth-first-searchbinary-tree
547	Number of Provinces	Medium	Graph	depth-first-searchbreadth-first-searchunion-findgraph
556	Next Greater Element III	Medium	Stack	mathtwo-pointersstring
557	Reverse Words in a String III	Easy	Strings	two-pointersstring
560	Subarray Sum Equals K	Medium	Arrays	arrayhash-tableprefix-sum
563	Binary Tree Tilt	Easy	Trees	treedepth-first-searchbinary-tree
566	Reshape the Matrix	Easy	Matrix	arraymatrixsimulation
570	Managers with at Least 5 Direct Reports	Medium	SQL	database
572	Subtree of Another Tree	Easy	Trees	treedepth-first-searchstring-matchingbinary-tree
577	Employee Bonus	Easy	SQL	database
584	Find Customer Referee	Easy	SQL	database
586	Customer Placing the Largest Number of Orders	Easy	Sorting	database
595	Big Countries	Easy	Trie	database
605	Can Place Flowers	Easy	LeetCode	arraygreedy
611	Valid Triangle Number	Medium	Dynamic Programming	arraytwo-pointersbinary-searchgreedy
617	Merge Two Binary Trees	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
619	Biggest Single Number	Easy	Bit Manipulation	database
620	Not Boring Movies	Easy	SQL	database
621	Task Scheduler	Medium	Greedy	arrayhash-tablegreedysorting
628	Maximum Product of Three Numbers	Easy	SQL	arraymathsorting
633	Sum of Square Numbers	Medium	Math	mathtwo-pointersbinary-search
637	Average of Levels in Binary Tree	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
643	Maximum Average Subarray I	Easy	Arrays	arraysliding-window
647	Palindromic Substrings	Medium	Strings	two-pointersstringdynamic-programming
658	Find K Closest Elements	Medium	LeetCode	arraytwo-pointersbinary-searchsliding-window
671	Second Minimum Node In a Binary Tree	Easy	Trees	treedepth-first-searchbinary-tree
678	Valid Parenthesis String	Medium	Strings	stringdynamic-programmingstackgreedy
680	Valid Palindrome II	Easy	Strings	two-pointersstringgreedy
682	Baseball Game	Easy	Stack	arraystacksimulation
692	Top K Frequent Words	Medium	Sorting	arrayhash-tablestringtrie
695	Max Area of Island	Medium	Graph	arraydepth-first-searchbreadth-first-searchunion-find
696	Count Binary Substrings	Easy	Strings	two-pointersstring
698	Partition to K Equal Sum Subsets	Medium	Dynamic Programming	arraydynamic-programmingbacktrackingbit-manipulation
713	Subarray Product Less Than K	Medium	Arrays	arraybinary-searchsliding-windowprefix-sum
718	Maximum Length of Repeated Subarray	Medium	Arrays	arraybinary-searchdynamic-programmingsliding-window
724	Pivot Index	Easy	Arrays	arrayprefix-sum
724	Find Pivot Index	Easy	LeetCode	arrayprefix-sum
733	Flood Fill	Easy	Graph	arraydepth-first-searchbreadth-first-searchmatrix
735	Asteroid Collision	Medium	Stack	arraystacksimulation
739	Daily Temperatures	Medium	SQL	arraystackmonotonic-stack
747	Min Cost Climbing Stairs	Easy	Dynamic Programming	arraydynamic-programming
753	Open the Lock	Medium	Graph	arrayhash-tablestringbreadth-first-search
764	N-ary Tree Level Order Traversal	Medium	Trees	treebreadth-first-search
767	Prime Number of Set Bits in Binary Representation	Easy	LeetCode	mathbit-manipulation
774	Maximum Depth of N-ary Tree	Easy	Trees	treedepth-first-searchbreadth-first-search
775	N-ary Tree Preorder Traversal	Easy	Trees	stacktreedepth-first-search
776	N-ary Tree Postorder Traversal	Easy	Trees	stacktreedepth-first-search
777	Toeplitz Matrix	Easy	Matrix	arraymatrix
778	Reorganize String	Medium	Strings	hash-tablestringgreedysorting
783	Search in a Binary Search Tree	Easy	Trees	treebinary-search-treebinary-tree
784	Insert into a Binary Search Tree	Medium	Trees	treebinary-search-treebinary-tree
789	Kth Largest Element in a Stream	Easy	Sorting	treedesignbinary-search-treeheap-priority-queue
792	Binary Search	Easy	LeetCode	arraybinary-search
795	K-th Symbol in Grammar	Medium	LeetCode	mathbit-manipulationrecursion
799	Minimum Distance Between BST Nodes	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-search-tree
800	Letter Case Permutation	Medium	LeetCode	stringbacktrackingbit-manipulation
812	Rotate String	Easy	Strings	stringstring-matching
837	Most Common Word	Easy	Strings	arrayhash-tablestringcounting
860	Design Circular Queue	Medium	Design	arraylinked-listdesignqueue
863	Sum of Distances in Tree	Hard	Trees	dynamic-programmingtreedepth-first-searchgraph
866	Rectangle Overlap	Easy	Math	mathgeometry
871	Keys and Rooms	Medium	Graph	depth-first-searchbreadth-first-searchgraph
878	Shifting Letters	Medium	LeetCode	arraystringprefix-sum
889	Buddy Strings	Easy	Strings	hash-tablestring
893	All Nodes Distance K in Binary Tree	Medium	Trees	hash-tabletreedepth-first-searchbreadth-first-search
898	Transpose Matrix	Easy	Matrix	arraymatrixsimulation
899	Binary Gap	Easy	Sorting	bit-manipulation
902	Minimum Number of Refueling Stops	Hard	LeetCode	arraydynamic-programminggreedyheap-priority-queue
908	Middle of the Linked List	Easy	Linked List	linked-listtwo-pointers
948	Sort an Array	Medium	LeetCode	arraydivide-and-conquersortingheap-priority-queue
951	Partition Array into Disjoint Intervals	Medium	Dynamic Programming	array
957	Minimum Add to Make Parentheses Valid	Medium	Strings	stringstackgreedy
965	Unique Email Addresses	Easy	SQL	arrayhash-tablestring
974	Reorder Data in Log Files	Medium	SQL	arraystringsorting
975	Range Sum of BST	Easy	Trees	treedepth-first-searchbinary-search-treebinary-tree
976	Minimum Area Rectangle	Medium	Math	arrayhash-tablemathgeometry
978	Longest Turbulent Subarray	—	Arrays
979	DI String Match	Easy	Strings	arraytwo-pointersstringgreedy
991	Array of Doubled Pairs	Medium	LeetCode	arrayhash-tablegreedysorting
998	Check Completeness of a Binary Tree	Medium	Trees	treebreadth-first-searchbinary-tree
1005	Univalued Binary Tree	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
1008	Binary Tree Cameras	Hard	Trees	dynamic-programmingtreedepth-first-searchbinary-tree
1013	Fibonacci Number	Easy	Math	mathdynamic-programmingrecursionmemoization
1014	K Closest Points to Origin	Medium	Heap	arraymathdivide-and-conquergeometry
1019	Squares of a Sorted Array	Easy	LeetCode	arraytwo-pointerssorting
1020	Longest Turbulent Subarray	Medium	Arrays	arraydynamic-programmingsliding-window
1021	Distribute Coins in Binary Tree	Medium	Trees	treedepth-first-searchbinary-tree
1026	String Without AAA or BBB	Medium	Strings	stringgreedy
1028	Interval List Intersections	Medium	Linked List	arraytwo-pointersline-sweep
1029	Vertical Order Traversal of a Binary Tree	Hard	Trees	hash-tabletreedepth-first-searchbreadth-first-search
1030	Smallest String Starting From Leaf	Medium	Strings	stringbacktrackingtreedepth-first-search
1034	Subarrays with K Different Integers	Hard	Arrays	arrayhash-tablesliding-windowcounting
1035	Cousins in Binary Tree	Easy	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
1039	Find the Town Judge	Easy	Graph	arrayhash-tablegraph
1046	Max Consecutive Ones III	Medium	LeetCode	arraybinary-searchsliding-windowprefix-sum
1054	Complement of Base 10 Integer	Easy	Math	bit-manipulation
1081	Video Stitching	Medium	Greedy	arraydynamic-programminggreedy
1217	Relative Sort Array	Easy	LeetCode	arrayhash-tablesortingcounting-sort
1222	Remove Covered Intervals	Medium	LeetCode	arraysorting
1241	Decompress Run-Length Encoded List	Easy	LeetCode	array
1250	Longest Common Subsequence	Medium	Dynamic Programming	stringdynamic-programming
1254	Deepest Leaves Sum	Medium	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
1267	Remove Zero Sum Consecutive Nodes from Linked List	Medium	Linked List	hash-tablelinked-list
1288	Maximum Subarray Sum with One Deletion	Medium	Arrays	arraydynamic-programming
1297	Maximum Number of Balloons	Easy	Dynamic Programming	hash-tablestringcounting
1304	Longest Happy String	Medium	Strings	stringgreedyheap-priority-queue
1349	Check If It Is a Straight Line	Easy	LeetCode	arraymathgeometry
1360	Maximum Length of a Concatenated String with Unique Characters	Medium	Strings	arraystringbacktrackingbit-manipulation
1370	Count Number of Nice Subarrays	Medium	Arrays	arrayhash-tablemathsliding-window
1380	Number of Closed Islands	Medium	Graph	arraydepth-first-searchbreadth-first-searchunion-find
1400	Find Winner on a Tic Tac Toe Game	Easy	LeetCode	arrayhash-tablematrixsimulation
1426	Find N Unique Integers Sum up to Zero	Easy	Math	arraymath
1428	Jump Game III	Medium	Greedy	arraydepth-first-searchbreadth-first-search
1437	Minimum Insertion Steps to Make a String Palindrome	Hard	Strings	stringdynamic-programming
1444	Number of Steps to Reduce a Number to Zero	Easy	Strings	mathbit-manipulation
1446	Angle Between Hands of a Clock	Medium	Math	math
1451	Minimum Number of Taps to Open to Water a Garden	Hard	LeetCode	arraydynamic-programminggreedy
1458	Sort Integers by The Number of 1 Bits	Easy	Bit Manipulation	arraybit-manipulationsortingcounting
1460	Number of Substrings Containing All Three Characters	Medium	Strings	hash-tablestringsliding-window
1468	Check If N and Its Double Exist	Easy	LeetCode	arrayhash-tabletwo-pointersbinary-search
1487	Cinema Seat Allocation	Medium	SQL	arrayhash-tablegreedybit-manipulation
1509	Replace Employee ID With The Unique Identifier	Easy	SQL	database
1544	Count Good Nodes in Binary Tree	Medium	Trees	treedepth-first-searchbreadth-first-searchbinary-tree
1570	Final Prices With a Special Discount in a Shop	Easy	LeetCode	arraystackmonotonic-stack
1635	Number of Good Pairs	Easy	LeetCode	arrayhash-tablemathcounting
1636	Number of Substrings With Only 1s	Medium	Strings	mathstring
1646	Kth Missing Positive Number	Easy	LeetCode	arraybinary-search
1648	Minimum Insertions to Balance a Parentheses String	Medium	Strings	stringstackgreedy
1677	Matrix Diagonal Sum	Easy	Matrix	arraymatrix
1700	Minimum Time to Make Rope Colorful	Medium	LeetCode	arraystringdynamic-programminggreedy
1720	Crawler Log Folder	Easy	Stack	arraystringstack
1738	Maximal Network Rank	Medium	Graph	graph
1770	Minimum Deletions to Make Character Frequencies Unique	Medium	LeetCode	hash-tablestringgreedysorting
1776	Minimum Operations to Reduce X to Zero	Medium	LeetCode	arrayhash-tablebinary-searchsliding-window
1777	Determine if Two Strings Are Close	Medium	Strings	hash-tablestringsortingcounting
1787	Sum of Absolute Differences in a Sorted Array	Medium	LeetCode	arraymathprefix-sum
1794	Minimize Deviation in Array	Hard	LeetCode	arraygreedyheap-priority-queueordered-set
1805	Minimum Adjacent Swaps for K Consecutive Ones	Hard	LeetCode	arraygreedysliding-windowprefix-sum
1829	Maximum Units on a Truck	Easy	Greedy	arraygreedysorting
1848	Sum of Unique Elements	Easy	LeetCode	arrayhash-tablecounting
1885	Count Number of Homogenous Substrings	Medium	Strings	mathstring
1915	Check if One String Swap Can Make Strings Equal	Easy	Strings	hash-tablestringcounting
1950	Sign of the Product of an Array	Easy	SQL	arraymath
1954	Replace All Digits with Characters	Easy	LeetCode	string
2035	Count Sub Islands	Medium	Graph	arraydepth-first-searchbreadth-first-searchunion-find
2053	Check if All Characters Have Equal Number of Occurrences	Easy	LeetCode	hash-tablestringcounting
2083	Three Divisors	Easy	Math	mathenumerationnumber-theory
2095	Minimum Number of Swaps to Make the String Balanced	Medium	Strings	two-pointersstringstackgreedy
2107	Find Unique Binary String	Medium	Strings	arrayhash-tablestringbacktracking
2113	Find the Kth Largest Integer in the Array	Medium	Sorting	arraystringdivide-and-conquersorting
2116	Count Number of Pairs With Absolute Difference K	Easy	LeetCode	arrayhash-tablecounting
2117	Find Original Array From Doubled Array	Medium	LeetCode	arrayhash-tablegreedysorting
2121	Find if Path Exists in Graph	Easy	Graph	depth-first-searchbreadth-first-searchunion-findgraph
2137	Final Value of Variable After Performing Operations	Easy	LeetCode	arraystringsimulation
2138	Sum of Beauty in the Array	Medium	LeetCode	array
2181	Smallest Index With Equal Value	Easy	LeetCode	array
2210	Find Target Indices After Sorting Array	Easy	LeetCode	arraybinary-searchsorting
2211	K Radius Subarray Averages	Medium	Arrays	arraysliding-window
2216	Delete the Middle Node of a Linked List	Medium	Linked List	linked-listtwo-pointers
2231	Find First Palindromic String in the Array	Easy	Strings	arraytwo-pointersstring
2233	Number of Smooth Descent Periods of a Stock	Medium	LeetCode	arraymathtwo-pointersdynamic-programming
2236	Maximum Twin Sum of a Linked List	Medium	Linked List	linked-listtwo-pointersstack
2238	A Number After a Double Reversal	Easy	LeetCode	math
2241	Recover the Original Array	Hard	Arrays	arrayhash-tabletwo-pointerssorting
2243	Check if All A's Appears Before All B's	Easy	LeetCode	string
2245	Destroying Asteroids	Medium	Greedy	arraygreedysorting
2284	Smallest Value of the Rearranged Number	Medium	LeetCode	mathsorting
2288	Count Operations to Obtain Zero	Easy	LeetCode	mathsimulation
2290	Removing Minimum Number of Magic Beans	Medium	LeetCode	arraygreedysortingenumeration
2298	Count Integers With Even Digit Sum	Easy	Math	mathsimulation
2383	Add Two Integers	Easy	Math	math
—	Activity Participants	—	LeetCode
—	Basic Calculator III	—	Stack
—	Binary Tree Longest Consecutive Sequence	—	Trees
—	Binary Tree Vertical Order Traversal	—	Trees
—	Boundary of Binary Tree	—	Trees
—	Check If a Number Is Majority Element in a Sorted Array	—	Arrays
—	Classes More Than 5 Students	—	SQL
—	Closest Binary Search Tree Value	—	Trees
—	Convert Binary Search Tree to Sorted Doubly Linked List	—	Trees
—	Correct a Binary Tree	—	Trees
—	Count Student Number in Departments	—	SQL
—	Count Univalue Subtrees	—	Trees
—	Counting Elements	—	LeetCode
—	Encode and Decode Strings	—	Strings
—	Find All The Lonely Nodes	—	Trees
—	Find Leaves of Binary Tree	—	Trees
—	Find the Celebrity	—	LeetCode
—	Graph Valid Tree	—	Graph
—	Group Shifted Strings	—	Strings
—	Implement strStr()	—	Strings
—	Inorder Successor in BST	—	Trees
—	Intersection of Three Sorted Arrays	—	Linked List
—	Logger Rate Limiter	—	Design
—	Longest Substring with At Most K Distinct Characters	—	Strings
—	Longest Substring with At Most Two Distinct Characters	—	Strings
—	Max Consecutive Ones II	—	LeetCode
—	Maximum Size Subarray Sum Equals k	—	Arrays
—	Meeting Rooms	—	Sorting
—	Meeting Rooms II	—	Sorting
—	Minimum Swaps to Group All 1's Together	—	LeetCode
—	Minimum Window Subsequence	—	Dynamic Programming
—	Missing Ranges	—	Arrays
—	Moving Average from Data Stream	—	Design
—	Next Palindrome Using Same Digits	—	Strings
—	Number of Connected Components in an Undirected Graph	—	Graph
—	Number of Distinct Islands	—	Graph
—	Palindrome Permutation	—	Strings
—	Permutations II (Unique)	—	Backtracking
—	Reverse Words in a String II	—	Strings
—	Search in a Sorted Array of Unknown Size	—	LeetCode
—	Serialize and Deserialize N-ary Tree	—	Trees
—	Shortest Word Distance	—	LeetCode
—	Shortest Word Distance II	—	LeetCode
—	Shortest Word Distance III	—	LeetCode
—	Sort Features by Popularity	—	LeetCode
—	Sorting Algorithms	—	Sorting
—	Split BST	—	Trees
—	String Permutations	—	Strings
—	Substrings That Begin and End With the Same Letter	—	Strings
—	Swap Salary	—	SQL
—	The Maze	—	Graph
—	Two Sum BSTs	—	Trees
—	Verify Preorder Sequence in Binary Search Tree	—	Trees
—	Walls and Gates	—	Matrix
—	Wiggle Sort	—	Sorting
—	Winning Candidate	—	SQL
—	Word Ladder	—	Graph
—	Word Search II	—	Trie