Array LeetCode Problems: All 1,569, With Python Solutions

Every problem in this library that LeetCode tags Array — 1,569 in total, 1,332 of them with a complete Python solution, a worked example and the time and space complexity of the approach.

1,569 problems
330 Easy
862 Medium
377 Hard

Array problems by difficulty

Showing the first 200 of 1,569 problems. Problems with a complete Python solution are listed first, then by ascending problem number.

Easy (31)

#	Problem	Difficulty	Topics
1	Two Sum	Easy	Array, Hash Table
14	Longest Common Prefix	Easy	Trie, Array, String
26	Remove Duplicates from Sorted Array	Easy	Array, Two Pointers
27	Remove Element	Easy	Array, Two Pointers
35	Search Insert Position	Easy	Array, Binary Search
66	Plus One	Easy	Array, Math
88	Merge Sorted Array	Easy	Array, Two Pointers, Sorting
108	Convert Sorted Array to Binary Search Tree	Easy	Tree, Binary Search Tree, Array +2
118	Pascal's Triangle	Easy	Array, Dynamic Programming
119	Pascal's Triangle II	Easy	Array, Dynamic Programming
121	Best Time to Buy and Sell Stock	Easy	Array, Dynamic Programming
136	Single Number	Easy	Bit Manipulation, Array
169	Majority Element	Easy	Array, Hash Table, Divide and Conquer +2
217	Contains Duplicate	Easy	Array, Hash Table, Sorting
219	Contains Duplicate II	Easy	Array, Hash Table, Sliding Window
228	Summary Ranges	Easy	Array
268	Missing Number	Easy	Bit Manipulation, Array, Hash Table +3
283	Move Zeroes	Easy	Array, Two Pointers
303	Range Sum Query - Immutable	Easy	Design, Array, Prefix Sum
349	Intersection of Two Arrays	Easy	Array, Hash Table, Two Pointers +2
350	Intersection of Two Arrays II	Easy	Array, Hash Table, Two Pointers +2
414	Third Maximum Number	Easy	Array, Sorting
448	Find All Numbers Disappeared in an Array	Easy	Array, Hash Table
455	Assign Cookies	Easy	Greedy, Array, Two Pointers +1
463	Island Perimeter	Easy	Depth-First Search, Breadth-First Search, Array +1
485	Max Consecutive Ones	Easy	Array
495	Teemo Attacking	Easy	Array, Simulation
496	Next Greater Element I	Easy	Stack, Array, Hash Table +1
500	Keyboard Row	Easy	Array, Hash Table, String
506	Relative Ranks	Easy	Array, Sorting, Heap (Priority Queue)
561	Array Partition	Easy	Greedy, Array, Counting Sort +1

Medium (128)

#	Problem	Difficulty	Topics
11	Container With Most Water	Medium	Greedy, Array, Two Pointers
15	3Sum	Medium	Array, Two Pointers, Sorting
16	3Sum Closest	Medium	Array, Two Pointers, Sorting
18	4Sum	Medium	Array, Two Pointers, Sorting
31	Next Permutation	Medium	Array, Two Pointers
33	Search in Rotated Sorted Array	Medium	Array, Binary Search
34	Find First and Last Position of Element in Sorted Array	Medium	Array, Binary Search
36	Valid Sudoku	Medium	Array, Hash Table, Matrix
39	Combination Sum	Medium	Array, Backtracking
40	Combination Sum II	Medium	Array, Backtracking
45	Jump Game II	Medium	Greedy, Array, Dynamic Programming
46	Permutations	Medium	Array, Backtracking
47	Permutations II	Medium	Array, Backtracking, Sorting
48	Rotate Image	Medium	Array, Math, Matrix
49	Group Anagrams	Medium	Array, Hash Table, String +1
53	Maximum Subarray	Medium	Array, Divide and Conquer, Dynamic Programming
54	Spiral Matrix	Medium	Array, Matrix, Simulation
55	Jump Game	Medium	Greedy, Array, Dynamic Programming
56	Merge Intervals	Medium	Array, Sorting
57	Insert Interval	Medium	Array
59	Spiral Matrix II	Medium	Array, Matrix, Simulation
63	Unique Paths II	Medium	Array, Dynamic Programming, Matrix
64	Minimum Path Sum	Medium	Array, Dynamic Programming, Matrix
73	Set Matrix Zeroes	Medium	Array, Hash Table, Matrix
74	Search a 2D Matrix	Medium	Array, Binary Search, Matrix
75	Sort Colors	Medium	Array, Two Pointers, Sorting
78	Subsets	Medium	Bit Manipulation, Array, Backtracking
79	Word Search	Medium	Depth-First Search, Array, String +2
80	Remove Duplicates from Sorted Array II	Medium	Array, Two Pointers
81	Search in Rotated Sorted Array II	Medium	Array, Binary Search
90	Subsets II	Medium	Bit Manipulation, Array, Backtracking
105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	Tree, Array, Hash Table +2
106	Construct Binary Tree from Inorder and Postorder Traversal	Medium	Tree, Array, Hash Table +2
120	Triangle	Medium	Array, Dynamic Programming
122	Best Time to Buy and Sell Stock II	Medium	Greedy, Array, Dynamic Programming
128	Longest Consecutive Sequence	Medium	Union Find, Array, Hash Table
130	Surrounded Regions	Medium	Depth-First Search, Breadth-First Search, Union Find +2
134	Gas Station	Medium	Greedy, Array
137	Single Number II	Medium	Bit Manipulation, Array
139	Word Break	Medium	Trie, Memoization, Array +3
150	Evaluate Reverse Polish Notation	Medium	Stack, Array, Math
152	Maximum Product Subarray	Medium	Array, Dynamic Programming
153	Find Minimum in Rotated Sorted Array	Medium	Array, Binary Search
162	Find Peak Element	Medium	Array, Binary Search
164	Maximum Gap	Medium	Array, Bucket Sort, Radix Sort +1
167	Two Sum II - Input Array Is Sorted	Medium	Array, Two Pointers, Binary Search
179	Largest Number	Medium	Greedy, Array, String +1
189	Rotate Array	Medium	Array, Math, Two Pointers
198	House Robber	Medium	Array, Dynamic Programming
200	Number of Islands	Medium	Depth-First Search, Breadth-First Search, Union Find +2
204	Count Primes	Medium	Array, Math, Enumeration +1
209	Minimum Size Subarray Sum	Medium	Array, Binary Search, Prefix Sum +1
213	House Robber II	Medium	Array, Dynamic Programming
215	Kth Largest Element in an Array	Medium	Array, Divide and Conquer, Quickselect +2
216	Combination Sum III	Medium	Array, Backtracking
221	Maximal Square	Medium	Array, Dynamic Programming, Matrix
229	Majority Element II	Medium	Array, Hash Table, Counting +1
238	Product of Array Except Self	Medium	Array, Prefix Sum
240	Search a 2D Matrix II	Medium	Array, Binary Search, Divide and Conquer +1
260	Single Number III	Medium	Bit Manipulation, Array
274	H-Index	Medium	Array, Counting Sort, Sorting
275	H-Index II	Medium	Array, Binary Search
284	Peeking Iterator	Medium	Design, Array, Iterator
287	Find the Duplicate Number	Medium	Bit Manipulation, Array, Two Pointers +1
289	Game of Life	Medium	Array, Matrix, Simulation
300	Longest Increasing Subsequence	Medium	Array, Binary Search, Dynamic Programming
304	Range Sum Query 2D - Immutable	Medium	Design, Array, Matrix +1
307	Range Sum Query - Mutable	Medium	Design, Binary Indexed Tree, Segment Tree +2
309	Best Time to Buy and Sell Stock with Cooldown	Medium	Array, Dynamic Programming
313	Super Ugly Number	Medium	Array, Math, Dynamic Programming
318	Maximum Product of Word Lengths	Medium	Bit Manipulation, Array, String
322	Coin Change	Medium	Breadth-First Search, Array, Dynamic Programming
324	Wiggle Sort II	Medium	Greedy, Array, Divide and Conquer +2
334	Increasing Triplet Subsequence	Medium	Greedy, Array
347	Top K Frequent Elements	Medium	Array, Hash Table, Divide and Conquer +5
368	Largest Divisible Subset	Medium	Array, Math, Dynamic Programming +1
373	Find K Pairs with Smallest Sums	Medium	Array, Heap (Priority Queue)
376	Wiggle Subsequence	Medium	Greedy, Array, Dynamic Programming
377	Combination Sum IV	Medium	Array, Dynamic Programming
378	Kth Smallest Element in a Sorted Matrix	Medium	Array, Binary Search, Matrix +2
380	Insert Delete GetRandom O(1)	Medium	Design, Array, Hash Table +2
384	Shuffle an Array	Medium	Design, Array, Math +1
393	UTF-8 Validation	Medium	Bit Manipulation, Array
396	Rotate Function	Medium	Array, Math, Dynamic Programming
399	Evaluate Division	Medium	Depth-First Search, Breadth-First Search, Union Find +4
406	Queue Reconstruction by Height	Medium	Binary Indexed Tree, Segment Tree, Array +1
413	Arithmetic Slices	Medium	Array, Dynamic Programming, Sliding Window
416	Partition Equal Subset Sum	Medium	Array, Dynamic Programming
417	Pacific Atlantic Water Flow	Medium	Depth-First Search, Breadth-First Search, Array +1
419	Battleships in a Board	Medium	Depth-First Search, Array, Matrix
421	Maximum XOR of Two Numbers in an Array	Medium	Bit Manipulation, Trie, Array +1
427	Construct Quad Tree	Medium	Tree, Array, Divide and Conquer +1
435	Non-overlapping Intervals	Medium	Greedy, Array, Dynamic Programming +1
436	Find Right Interval	Medium	Array, Binary Search, Sorting
442	Find All Duplicates in an Array	Medium	Array, Hash Table, Sorting
447	Number of Boomerangs	Medium	Array, Hash Table, Math
452	Minimum Number of Arrows to Burst Balloons	Medium	Greedy, Array, Sorting
453	Minimum Moves to Equal Array Elements	Medium	Array, Math
454	4Sum II	Medium	Array, Hash Table
456	132 Pattern	Medium	Stack, Array, Binary Search +2
457	Circular Array Loop	Medium	Array, Hash Table, Two Pointers
462	Minimum Moves to Equal Array Elements II	Medium	Array, Math, Sorting
473	Matchsticks to Square	Medium	Bit Manipulation, Array, Dynamic Programming +2
474	Ones and Zeroes	Medium	Array, String, Dynamic Programming
475	Heaters	Medium	Array, Two Pointers, Binary Search +1
477	Total Hamming Distance	Medium	Bit Manipulation, Array, Math
486	Predict the Winner	Medium	Recursion, Array, Math +2
491	Non-decreasing Subsequences	Medium	Bit Manipulation, Array, Hash Table +1
494	Target Sum	Medium	Array, Dynamic Programming, Backtracking
497	Random Point in Non-overlapping Rectangles	Medium	Reservoir Sampling, Array, Math +4
498	Diagonal Traverse	Medium	Array, Matrix, Simulation
503	Next Greater Element II	Medium	Stack, Array, Monotonic Stack
518	Coin Change II	Medium	Array, Dynamic Programming
522	Longest Uncommon Subsequence II	Medium	Array, Hash Table, Two Pointers +2
523	Continuous Subarray Sum	Medium	Array, Hash Table, Math +1
524	Longest Word in Dictionary through Deleting	Medium	Array, Two Pointers, String +1
525	Contiguous Array	Medium	Array, Hash Table, Prefix Sum
526	Beautiful Arrangement	Medium	Bit Manipulation, Array, Dynamic Programming +2
528	Random Pick with Weight	Medium	Array, Math, Binary Search +2
529	Minesweeper	Medium	Depth-First Search, Breadth-First Search, Array +1
532	K-diff Pairs in an Array	Medium	Array, Hash Table, Two Pointers +2
539	Minimum Time Difference	Medium	Array, Math, String +1
540	Single Element in a Sorted Array	Medium	Array, Binary Search
542	01 Matrix	Medium	Breadth-First Search, Array, Dynamic Programming +1
553	Optimal Division	Medium	Array, Math, Dynamic Programming
554	Brick Wall	Medium	Array, Hash Table
560	Subarray Sum Equals K	Medium	Array, Hash Table, Prefix Sum
565	Array Nesting	Medium	Depth-First Search, Array

Hard (41)

#	Problem	Difficulty	Topics
4	Median of Two Sorted Arrays	Hard	Array, Binary Search, Divide and Conquer
37	Sudoku Solver	Hard	Array, Hash Table, Backtracking +1
41	First Missing Positive	Hard	Array, Hash Table
42	Trapping Rain Water	Hard	Stack, Array, Two Pointers +2
51	N-Queens	Hard	Array, Backtracking
68	Text Justification	Hard	Array, String, Simulation
84	Largest Rectangle in Histogram	Hard	Stack, Array, Monotonic Stack
85	Maximal Rectangle	Hard	Stack, Array, Dynamic Programming +2
123	Best Time to Buy and Sell Stock III	Hard	Array, Dynamic Programming
135	Candy	Hard	Greedy, Array
140	Word Break II	Hard	Trie, Memoization, Array +4
149	Max Points on a Line	Hard	Geometry, Array, Hash Table +1
154	Find Minimum in Rotated Sorted Array II	Hard	Array, Binary Search
174	Dungeon Game	Hard	Array, Dynamic Programming, Matrix
188	Best Time to Buy and Sell Stock IV	Hard	Array, Dynamic Programming
212	Word Search II	Hard	Trie, Array, String +2
218	The Skyline Problem	Hard	Binary Indexed Tree, Segment Tree, Array +5
220	Contains Duplicate III	Hard	Array, Bucket Sort, Ordered Set +2
239	Sliding Window Maximum	Hard	Queue, Array, Sliding Window +2
312	Burst Balloons	Hard	Array, Dynamic Programming
315	Count of Smaller Numbers After Self	Hard	Binary Indexed Tree, Segment Tree, Array +4
321	Create Maximum Number	Hard	Stack, Greedy, Array +2
327	Count of Range Sum	Hard	Binary Indexed Tree, Segment Tree, Array +4
329	Longest Increasing Path in a Matrix	Hard	Depth-First Search, Breadth-First Search, Graph +5
330	Patching Array	Hard	Greedy, Array
335	Self Crossing	Hard	Geometry, Array, Math
336	Palindrome Pairs	Hard	Trie, Array, Hash Table +1
354	Russian Doll Envelopes	Hard	Array, Binary Search, Dynamic Programming +1
363	Max Sum of Rectangle No Larger Than K	Hard	Array, Binary Search, Matrix +2
381	Insert Delete GetRandom O(1) - Duplicates allowed	Hard	Design, Array, Hash Table +2
391	Perfect Rectangle	Hard	Geometry, Array, Hash Table +2
403	Frog Jump	Hard	Array, Dynamic Programming
407	Trapping Rain Water II	Hard	Breadth-First Search, Array, Matrix +1
410	Split Array Largest Sum	Hard	Greedy, Array, Binary Search +2
446	Arithmetic Slices II - Subsequence	Hard	Array, Dynamic Programming
472	Concatenated Words	Hard	Depth-First Search, Trie, Array +3
480	Sliding Window Median	Hard	Array, Hash Table, Sliding Window +1
493	Reverse Pairs	Hard	Binary Indexed Tree, Segment Tree, Array +4
502	IPO	Hard	Greedy, Array, Sorting +1
517	Super Washing Machines	Hard	Greedy, Array
546	Remove Boxes	Hard	Memoization, Array, Dynamic Programming

When the Array problem arrives live

Stealth Interview is a desktop app for macOS and Windows. It reads the coding problem off your screen, returns a working solution with a step-by-step explanation and its time and space complexity, and transcribes what the interviewer is saying — while staying invisible to screen sharing.

Get Stealth Interview See pricing