Interview Problems

Practice coding problems with detailed solutions and explanations

Ranking	Problem	Difficulty	Companies	Topics	Frequency
#1	Two Sum	Easy	+6 more	Array Tabla Hash	95%
#2	Valid Parentheses	Easy	+6 more	Cadena Pila	89%
#3	Best Time to Buy and Sell Stock	Easy	+6 more	Array Programación Dinámica	87%
#4	Merge Two Sorted Lists	Easy	+6 more	Lista Enlazada Recursión	84%
#5	Valid Anagram	Easy	+6 more	Tabla Hash Cadena +1 more	82%
#6	Binary Search	Easy	+6 more	Array Búsqueda Binaria	80%
#7	Reverse Linked List	Easy	+6 more	Lista Enlazada Recursión	78%
#8	Contains Duplicate	Easy	+6 more	Array Tabla Hash +1 more	76%
#9	Maximum Subarray	Medium	+6 more	Array Divide y Vencerás +1 more	74%
#10	3Sum	Medium	+6 more	Array Dos Punteros +1 more	72%
#11	Climbing Stairs	Easy	+6 more	Matemáticas Programación Dinámica +1 more	70%
#12	Longest Palindromic Substring	Medium	+6 more	Cadena Programación Dinámica	68%
#13	Product of Array Except Self	Medium	+6 more	Array Suma de Prefijos	66%
#14	Group Anagrams	Medium	+6 more	Array Tabla Hash +2 more	64%
#15	Top K Frequent Elements	Medium	+6 more	Array Tabla Hash +6 more	62%
#16	Palindromic Substrings	Medium	+4 more	Cadena Programación Dinámica	68%
#17	Course Schedule	Medium	+5 more	Búsqueda en Profundidad Búsqueda en Amplitud +2 more	75%
#18	House Robber	Medium	+5 more	Array Programación Dinámica	82%
#19	Meeting Rooms II	Medium	+6 more	Array Dos Punteros +3 more	88%
#20	Implement Trie (Prefix Tree)	Medium	+6 more	Tabla Hash Cadena +2 more	79%
#21	Lowest Common Ancestor of a Binary Tree	Medium	+6 more	Árbol Búsqueda en Profundidad +1 more	85%
#22	Word Search	Medium	+6 more	Array Backtracking +1 more	77%
#23	Subarray Sum Equals K	Medium	+6 more	Array Tabla Hash +1 more	81%
#24	Spiral Matrix	Medium	+6 more	Array Matriz +1 more	73%
#25	Decode Ways	Medium	+6 more	Cadena Programación Dinámica	69%
#26	Find Minimum in Rotated Sorted Array	Medium	+6 more	Array Búsqueda Binaria	84%
#27	Kth Largest Element in an Array	Medium	+6 more	Array Divide y Vencerás +3 more	91%
#28	Combination Sum	Medium	+6 more	Array Backtracking	78%
#29	Number of Islands	Medium	+6 more	Array Búsqueda en Profundidad +3 more	89%
#30	Longest Substring Without Repeating Characters	Medium	+6 more	Tabla Hash Cadena +1 more	93%
#31	Container With Most Water	Medium	+6 more	Array Dos Punteros +1 more	86%
#32	Merge Intervals	Medium	+6 more	Array Ordenación	87%
#33	Rotate Array	Medium	+6 more	Array Matemáticas +1 more	72%
#34	Search in Rotated Sorted Array	Medium	+6 more	Array Búsqueda Binaria	88%
#35	Permutations	Medium	+6 more	Array Backtracking	79%
#36	Jump Game	Medium	+6 more	Array Programación Dinámica +1 more	83%
#37	Unique Paths	Medium	+6 more	Matemáticas Programación Dinámica +1 more	76%
#38	Set Matrix Zeroes	Medium	+6 more	Array Tabla Hash +1 more	71%
#39	Minimum Window Substring	Hard	+6 more	Tabla Hash Cadena +1 more	85%
#40	Coin Change	Medium	+6 more	Array Programación Dinámica +1 more	90%
#41	Word Break	Medium	+6 more	Tabla Hash Cadena +2 more	83%
#42	Longest Common Subsequence	Medium	+6 more	String Dynamic Programming	81%
#43	Edit Distance	Medium	+6 more	String Dynamic Programming	77%
#44	Trapping Rain Water	Hard	+6 more	Array Two Pointers +2 more	92%
#45	Clone Graph	Medium	+6 more	Hash Table Depth-First Search +2 more	78%
#46	Pacific Atlantic Water Flow	Medium	+6 more	Array Depth-First Search +2 more	71%
#47	Alien Dictionary	Hard	+6 more	Array String +4 more	74%
#48	Graph Valid Tree	Medium	+6 more	Depth-First Search Breadth-First Search +2 more	69%
#49	Number of Connected Components	Medium	+6 more	Depth-First Search Breadth-First Search +2 more	76%
#50	Longest Increasing Subsequence	Medium	+6 more	Array Binary Search +1 more	84%
#51	Maximum Subarray	Easy	+6 more	Array Divide and Conquer +1 more	92%
#52	Climbing Stairs	Easy	+6 more	Math Dynamic Programming +1 more	88%
#53	Best Time to Buy and Sell Stock	Easy	+6 more	Array Dynamic Programming	90%
#54	Maximum Depth of Binary Tree	Easy	+6 more	Tree Depth-First Search +2 more	85%
#55	Same Tree	Easy	+6 more	Tree Depth-First Search +2 more	82%
#56	Symmetric Tree	Easy	+6 more	Tree Depth-First Search +2 more	80%
#57	Path Sum	Easy	+6 more	Tree Depth-First Search +2 more	78%
#58	Minimum Depth of Binary Tree	Easy	+6 more	Tree Depth-First Search +2 more	76%
#59	Balanced Binary Tree	Easy	+6 more	Tree Depth-First Search +1 more	74%
#60	Convert Sorted Array to Binary Search Tree	Easy	+6 more	Array Divide and Conquer +3 more	72%
#61	Merge Two Sorted Lists	Easy	+6 more	Linked List Recursion	70%
#62	Remove Duplicates from Sorted List	Easy	+6 more	Linked List	68%
#63	Linked List Cycle	Easy	+6 more	Hash Table Linked List +1 more	66%
#64	Binary Tree Inorder Traversal	Easy	+6 more	Stack Tree +2 more	64%
#65	Symmetric Tree	Easy	+6 more	Tree Depth-First Search +2 more	62%
#66	Binary Tree Level Order Traversal	Medium	+6 more	Tree Breadth-First Search +1 more	60%
#67	Binary Tree Zigzag Level Order Traversal	Medium	+6 more	Tree Breadth-First Search +1 more	58%
#68	Construct Binary Tree from Preorder and Inorder Traversal	Medium	+6 more	Array Hash Table +3 more	56%
#69	Populating Next Right Pointers in Each Node	Medium	+6 more	Tree Depth-First Search +2 more	54%
#70	Sum of Left Leaves	Easy	+6 more	Tree Depth-First Search +2 more	52%
#71	Find All Anagrams in a String	Medium	+6 more	Hash Table String +1 more	50%
#72	Permutation in String	Medium	+6 more	Hash Table Two Pointers +2 more	48%
#73	Longest Substring Without Repeating Characters	Medium	+6 more	Hash Table String +1 more	46%
#74	Minimum Window Substring	Hard	+6 more	Hash Table String +1 more	44%
#75	Sliding Window Maximum	Hard	+6 more	Array Queue +3 more	42%
#76	Single Number	Easy	+1 more	Array Bit Manipulation	85%
#77	Number of 1 Bits	Easy		Bit Manipulation Divide and Conquer	70%
#78	Counting Bits	Easy		Dynamic Programming Bit Manipulation	68%
#79	Sum of Two Integers	Medium		Math Bit Manipulation	60%
#80	Gas Station	Medium		Array Greedy	75%
#81	Partition Labels	Medium		Hash Table String +2 more	72%
#82	Task Scheduler	Medium		Array Hash Table +4 more	80%
#83	Jump Game II	Medium		Array Dynamic Programming +1 more	78%
#84	Hand of Straights	Medium		Array Hash Table +2 more	65%
#85	Min Stack	Medium		Stack Design	88%
#86	Daily Temperatures	Medium		Array Stack +1 more	82%
#87	Largest Rectangle in Histogram	Hard		Array Stack +1 more	75%
#88	Merge K Sorted Lists	Hard	+1 more	Linked List Divide and Conquer +2 more	90%
#89	Find Median from Data Stream	Hard		Two Pointers Design +3 more	85%
#90	K Closest Points to Origin	Medium		Array Math +5 more	83%
#91	Insert Interval	Medium		Array	88%
#92	Non-overlapping Intervals	Medium		Array Dynamic Programming +2 more	78%
#93	Meeting Rooms	Easy		Array Sorting	70%
#94	Design Add and Search Words Data Structure	Medium		String Depth-First Search +2 more	75%
#95	Word Search II	Hard		Array String +3 more	80%

Interview Problems

Two Sum

Valid Parentheses

Best Time to Buy and Sell Stock

Merge Two Sorted Lists

Valid Anagram

Binary Search

Reverse Linked List

Contains Duplicate

Maximum Subarray

3Sum

Climbing Stairs

Longest Palindromic Substring

Product of Array Except Self

Group Anagrams

Top K Frequent Elements

Palindromic Substrings

Course Schedule

House Robber

Meeting Rooms II

Implement Trie (Prefix Tree)

Lowest Common Ancestor of a Binary Tree

Word Search

Subarray Sum Equals K

Spiral Matrix

Decode Ways

Find Minimum in Rotated Sorted Array

Kth Largest Element in an Array

Combination Sum

Number of Islands

Longest Substring Without Repeating Characters

Container With Most Water

Merge Intervals

Rotate Array

Search in Rotated Sorted Array

Permutations

Jump Game

Unique Paths

Set Matrix Zeroes

Minimum Window Substring

Coin Change

Word Break

Longest Common Subsequence

Edit Distance

Trapping Rain Water

Clone Graph

Pacific Atlantic Water Flow

Alien Dictionary

Graph Valid Tree

Number of Connected Components

Longest Increasing Subsequence

Maximum Subarray

Climbing Stairs

Best Time to Buy and Sell Stock

Maximum Depth of Binary Tree

Same Tree

Symmetric Tree

Path Sum

Minimum Depth of Binary Tree

Balanced Binary Tree

Convert Sorted Array to Binary Search Tree

Merge Two Sorted Lists

Remove Duplicates from Sorted List

Linked List Cycle

Binary Tree Inorder Traversal

Symmetric Tree

Binary Tree Level Order Traversal

Binary Tree Zigzag Level Order Traversal

Construct Binary Tree from Preorder and Inorder Traversal

Populating Next Right Pointers in Each Node

Sum of Left Leaves

Find All Anagrams in a String

Permutation in String

Longest Substring Without Repeating Characters

Minimum Window Substring

Sliding Window Maximum

Single Number

Number of 1 Bits

Counting Bits

Sum of Two Integers