LeetCode Problems

2,913 practice problems · Browse by topic and difficulty

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Array1674 String699 Hash Table611 Dynamic Programming530 Math528 Sorting400 Greedy377 Binary Search265 Depth-First Search253 Matrix221 Bit Manipulation220 Breadth-First Search197 Tree191 Prefix Sum186 Two Pointers182 Simulation171 Heap (Priority Queue)169 Counting149 Graph141 Stack140 Sliding Window133 Binary Tree130 Enumeration118 Database96 Design94 Backtracking88 Union Find74 Number Theory73 Linked List66 Ordered Set59 Segment Tree57 Monotonic Stack54 Combinatorics49 Bitmask47 Trie45 Divide and Conquer42 Memoization41 Queue40 Recursion40 Geometry38 Binary Indexed Tree33 String Matching33 Hash Function31 Binary Search Tree29 Shortest Path29 Topological Sort28 Rolling Hash25 Game Theory24 Monotonic Queue18 Brainteaser16 Data Stream13 Randomized12 Counting Sort9 Doubly-Linked List9 Merge Sort9 Quickselect7 Bucket Sort6 Concurrency6 Line Sweep6 Probability and Statistics6 Interactive5 Iterator5 Suffix Array5 Reservoir Sampling4 Shell4 Eulerian Circuit3 Minimum Spanning Tree3 Radix Sort3 Strongly Connected Component3 Rejection Sampling2 Sort2 Biconnected Component1

More practice problems

Browse 62 additional practice problems

Add Two Promises Allow One Function Call Apply Transform Over Each Element in Array Array Reduce Transformation Array Wrapper Cache With Time Limit Calculator with Method Chaining Call Function with Custom Context Change Data Type Check if Object Instance of Class Chunk Array Compact Object Counter Counter II Create a DataFrame from List Create a New Column Create Hello World Function Debounce Design Cancellable Function Display the First Three Rows Drop Duplicate Rows Drop Missing Data Earliest Finish Time for Land and Water Rides I Earliest Finish Time for Land and Water Rides II Event Emitter Execute Asynchronous Functions in Parallel Fill Missing Data Filter Elements from Array Flatten Deeply Nested Array Function Composition Generate Fibonacci Sequence Get the Size of a DataFrame Group By Interval Cancellation Is Object Empty Join Two Arrays by ID Maximum Balanced Shipments Maximum Median Sum of Subsequences of Size 3 Maximum Number of Subsequences After One Inserting Memoize Memoize II Method Chaining Minimum Jumps to Reach End via Prime Teleportation Minimum Removals to Balance Array Minimum Time to Activate String Modify Columns Nested Array Generator Promise Time Limit Rename Columns Reshape Data: Concatenate Reshape Data: Melt Reshape Data: Pivot Return Length of Arguments Passed Select Data Sleep Snail Traversal Sort By Threshold Majority Queries Timeout Cancellation To Be Or Not To Be Trionic Array I Trionic Array II

#	Title	Topics	Difficulty
1	Two Sum	ArrayHash Table	Easy
2	Add Two Numbers	Linked ListMathRecursion	Medium
3	Longest Substring Without Repeating Characters	Hash TableStringSliding Window	Medium
4	Median of Two Sorted Arrays	ArrayBinary SearchDivide and Conquer	Hard
5	Longest Palindromic Substring	Two PointersStringDynamic Programming	Medium
6	Zigzag Conversion	String	Medium
7	Reverse Integer	Math	Medium
8	String to Integer (atoi)	String	Medium
9	Palindrome Number	Math	Easy
10	Regular Expression Matching	StringDynamic ProgrammingRecursion	Hard
11	Container With Most Water	ArrayTwo PointersGreedy	Medium
12	Integer to Roman	Hash TableMathString	Medium
13	Roman to Integer	Hash TableMathString	Easy
14	Longest Common Prefix	ArrayStringTrie	Easy
15	3Sum	ArrayTwo PointersSorting	Medium
16	3Sum Closest	ArrayTwo PointersSorting	Medium
17	Letter Combinations of a Phone Number	Hash TableStringBacktracking	Medium
18	4Sum	ArrayTwo PointersSorting	Medium
19	Remove Nth Node From End of List	Linked ListTwo Pointers	Medium
20	Valid Parentheses	StringStack	Easy
21	Merge Two Sorted Lists	Linked ListRecursion	Easy
22	Generate Parentheses	StringDynamic ProgrammingBacktracking	Medium
23	Merge k Sorted Lists	Linked ListDivide and ConquerHeap (Priority Queue)+1	Hard
24	Swap Nodes in Pairs	Linked ListRecursion	Medium
25	Reverse Nodes in k-Group	Linked ListRecursion	Hard
26	Remove Duplicates from Sorted Array	ArrayTwo Pointers	Easy
27	Remove Element	ArrayTwo Pointers	Easy
28	Find the Index of the First Occurrence in a String	Two PointersStringString Matching	Easy
29	Divide Two Integers	MathBit Manipulation	Medium
30	Substring with Concatenation of All Words	Hash TableStringSliding Window	Hard
31	Next Permutation	ArrayTwo Pointers	Medium
32	Longest Valid Parentheses	StringDynamic ProgrammingStack	Hard
33	Search in Rotated Sorted Array	ArrayBinary Search	Medium
34	Find First and Last Position of Element in Sorted Array	ArrayBinary Search	Medium
35	Search Insert Position	ArrayBinary Search	Easy
36	Valid Sudoku	ArrayHash TableMatrix	Medium
37	Sudoku Solver	ArrayHash TableBacktracking+1	Hard
38	Count and Say	String	Medium
39	Combination Sum	ArrayBacktracking	Medium
40	Combination Sum II	ArrayBacktracking	Medium
41	First Missing Positive	ArrayHash Table	Hard
42	Trapping Rain Water	ArrayTwo PointersDynamic Programming+2	Hard
43	Multiply Strings	MathStringSimulation	Medium
44	Wildcard Matching	StringDynamic ProgrammingGreedy+1	Hard
45	Jump Game II	ArrayDynamic ProgrammingGreedy	Medium
46	Permutations	ArrayBacktracking	Medium
47	Permutations II	ArrayBacktrackingSorting	Medium
48	Rotate Image	ArrayMathMatrix	Medium
49	Group Anagrams	ArrayHash TableString+1	Medium
50	Pow(x, n)	MathRecursion	Medium

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