neetcode 75

Question 1

Two Sum

Answer 1

Find two numbers that add up to a specific target.

Question 2

Valid Anagram

Answer 2

Determine if two strings are anagrams of each other.

Question 3

Group Anagrams

Answer 3

Group a list of strings into anagrams.

Question 4

Top K Frequent Elements

Answer 4

Find the k most frequent elements in an array.

Question 5

Product of Array Except Self

Answer 5

Calculate the product of an array except self.

Question 6

Valid Sudoku

Answer 6

Determine if a Sudoku is valid.

Question 7

Encode and Decode Strings

Answer 7

Encode and decode strings for transmission.

Question 8

Longest Consecutive Sequence

Answer 8

Find the length of the longest consecutive elements sequence.

Question 9

Valid Palindrome

Answer 9

Check if a string is a palindrome.

Question 10

Three Sum

Answer 10

Find all unique triplets in an array that sum to zero.

Question 11

Container With Most Water

Answer 11

Find the maximum area of water that can be contained.

Question 12

Trapping Rain Water

Answer 12

Calculate how much water can be trapped after raining.

Question 13

Best Time to Buy and Sell Stock

Answer 13

Find the best time to buy and sell stock for maximum profit.

Question 14

Longest Substring Without Repeating Characters

Answer 14

Find the length of the longest substring without repeating characters.

Question 15

Longest Repeating Character Replacement

Answer 15

Find the length of the longest substring after replacement.

Question 16

Minimum Window Substring

Answer 16

Find the minimum window substring containing all characters.

Question 17

Sliding Window Maximum

Answer 17

Find the maximum value in each sliding window.

Question 18

Valid Parentheses

Answer 18

Check if parentheses are valid.

Question 19

Min Stack

Answer 19

Design a stack that supports push, pop, top, and retrieving the minimum element.

Question 20

Evaluate Reverse Polish Notation

Answer 20

Evaluate an expression in Reverse Polish Notation.

Question 21

Generate Parentheses

Answer 21

Generate all combinations of well-formed parentheses.

Question 22

Daily Temperatures

Answer 22

Find how many days until a warmer temperature.

Question 23

Car Fleet

Answer 23

Calculate the number of car fleets that will arrive at the destination.

Question 24

Largest Rectangle in Histogram

Answer 24

Find the area of the largest rectangle in a histogram.

Question 25

Binary Search

Answer 25

Perform binary search on a sorted array.

Question 26

Search a 2D Matrix

Answer 26

Search for a target value in a 2D matrix.

Question 27

Koko Eating Bananas

Answer 27

Determine the minimum eating speed for Koko.

Question 28

Find Minimum in Rotated Sorted Array

Answer 28

Find the minimum element in a rotated sorted array.

Question 29

Search in Rotated Sorted Array

Answer 29

Search for a target in a rotated sorted array.

Question 30

Time Based Key-Value Store

Answer 30

Implement a time-based key-value store.

Question 31

Median of Two Sorted Arrays

Answer 31

Find the median of two sorted arrays.

Question 32

Reverse Linked List

Answer 32

Reverse a singly linked list.

Question 33

Merge Two Sorted Lists

Answer 33

Merge two sorted linked lists into one sorted list.

Question 34

Reorder List

Answer 34

Reorder a linked list in a specific pattern.

Question 35

Remove Nth Node From End of List

Answer 35

Remove the nth node from the end of a linked list.

Question 36

Copy List with Random Pointer

Answer 36

Create a deep copy of a linked list with random pointers.

Question 37

Add Two Numbers

Answer 37

Add two numbers represented by linked lists.

Question 38

Linked List Cycle

Answer 38

Determine if a linked list has a cycle.

Question 39

Find the Duplicate Number

Answer 39

Find the duplicate number in an array.

Question 40

LRU Cache

Answer 40

Design a Least Recently Used (LRU) cache.

Question 41

Merge K Sorted Lists

Answer 41

Merge k sorted linked lists into one sorted list.

Question 42

Reverse Nodes in K Group

Answer 42

Reverse nodes in k-group in a linked list.

Question 43

Invert Binary Tree

Answer 43

Invert a binary tree.

Question 44

Maximum Depth of Binary Tree

Answer 44

Find the maximum depth of a binary tree.

Question 45

Diameter of Binary Tree

Answer 45

Calculate the diameter of a binary tree.

Question 46

Balanced Binary Tree

Answer 46

Check if a binary tree is balanced.

Question 47

Same Tree

Answer 47

Check if two binary trees are the same.

Question 48

Subtree of Another Tree

Answer 48

Check if one tree is a subtree of another.

Question 49

Lowest Common Ancestor of a BST

Answer 49

Find the lowest common ancestor in a binary search tree.

Question 50

Binary Tree Level Order Traversal

Answer 50

Perform level order traversal of a binary tree.

Question 51

Binary Tree Right Side View

Answer 51

Get the right side view of a binary tree.

Question 52

Count Good Nodes in Binary Tree

Answer 52

Count the number of good nodes in a binary tree.

Question 53

Validate Binary Search Tree

Answer 53

Check if a binary tree is a valid binary search tree.

Question 54

Kth Smallest Element in a BST

Answer 54

Find the kth smallest element in a binary search tree.

Question 55

Construct Binary Tree from Preorder and Inorder Traversal

Answer 55

Construct a binary tree from preorder and inorder traversal.

Question 56

Binary Tree Maximum Path Sum

Answer 56

Find the maximum path sum in a binary tree.

Question 57

Serialize and Deserialize Binary Tree

Answer 57

Serialize and deserialize a binary tree.

Question 58

Implement Trie (Prefix Tree)

Answer 58

Implement a trie data structure.

Question 59

Design Add and Search Words Data Structure

Answer 59

Design a data structure to add and search words.

Question 60

Word Search II

Answer 60

Find all words in a board using a trie.

Question 61

Kth Largest Element in a Stream

Answer 61

Find the kth largest element in a stream of numbers.

Question 62

Last Stone Weight

Answer 62

Calculate the weight of the last stone after smashing.

Question 63

K Closest Points to Origin

Answer 63

Find the k closest points to the origin.

Question 64

Kth Largest Element in an Array

Answer 64

Find the kth largest element in an array.

Question 65

Task Scheduler

Answer 65

Schedule tasks with a given cooldown.

Question 66

Design Twitter

Answer 66

Design a Twitter-like system.

Question 67

Find Median from Data Stream

Answer 67

Find the median from a data stream.

Question 68

Subsets

Answer 68

Generate all subsets of a set.

Question 69

Combination Sum

Answer 69

Find all combinations that sum to a target.

Question 70

Permutations

Answer 70

Generate all permutations of a set.

Question 71

Subsets II (Duplicates)

Answer 71

Generate all subsets including duplicates.

Question 72

Combination Sum II

Answer 72

Find all unique combinations that sum to a target.

Question 73

Word Search

Answer 73

Search for a word in a 2D board.

Question 74

Palindrome Partitioning

Answer 74

Partition a string into palindromic substrings.

Question 75

Letter Combinations of a Phone Number

Answer 75

Generate all letter combinations from a phone number.