Problems

48 problems

• Easy

  Reverse Integer

  Given a signed 32-bit integer x, return x with its digits reversed. …

• Easy

  Roman to Integer

  Roman numerals are represented by seven different symbols: I, V, X, L, …

• Easy

  FizzBuzz

  Given an integer n, print numbers from 1 to n, but: - …

• Easy

  Longest Common Prefix

  Write a function to find the longest common prefix string amongst an …

• Easy

  Reverse String

  Write a function that reverses a string. The input string is given …

• Easy

  Valid Parentheses

  Given a string s containing just the characters '(', ')', '{', '}', …

• Easy

  Palindrome Number

  Given an integer x, return true if x is a palindrome, and …

• Easy

  Binary Search

  Given an array of integers nums which is sorted in ascending order, …

• Easy

  Fibonacci Number

  Given an integer n, output the nth Fibonacci number. The Fibonacci sequence …

• Easy

  Prime Check

  Given an integer n, determine if it is a prime number. Output …

• Easy

  Maximum Average Subarray I

  You are given an integer array nums consisting of n elements, and …

  Sliding Window
• Easy

  Single Number

  Given a non-empty array of integers nums, every element appears twice except …

  Bit Manipulation
• Easy

  Number of 1 Bits

  Write a function that takes the binary representation of a positive integer …

  Bit Manipulation
• Easy

  Counting Bits

  Given an integer n, return an array ans of length n + …

  Bit Manipulation
• Easy

  Climbing Stairs

  You are climbing a staircase. It takes n steps to reach the …

  Math
• Easy

  Merge Sorted Array

  You are given two integer arrays nums1 and nums2, sorted in non-decreasing …

  Sorting
• Easy

  Reverse Words

  Given a sentence (a string of words separated by single spaces), reverse …

• Easy

  Pascal Triangle Row

  Given a row number n (0-indexed), return the nth row of Pascal's …

• Easy

  GCD of Two Numbers

  Given two positive integers a and b, find their Greatest Common Divisor …

  Math
• Easy

  Two Sum

  Given an array of integers nums and an integer target, return indices …

  Arrays Hashing
• Easy

  Valid Anagram

  Given two strings s and t, return true if t is an …

  Hashing Strings
• Easy

  Best Time to Buy and Sell Stock

  You are given an array prices where prices[i] is the price of …

  Arrays Dynamic Programming
• Easy

  Contains Duplicate

  Given an integer array nums, return true if any value appears at …

  Arrays Hashing
• Easy

  Move Zeroes

  Given an integer array nums, move all 0's to the end of …

  Arrays Two Pointers
• Medium

  Maximum Subarray

  Given an integer array nums, find the subarray with the largest sum, …

• Medium

  Container With Most Water

  You are given an integer array height of length n. There are …

• Medium

  Longest Substring Without Repeating Characters

  Given a string s, find the length of the longest substring without …

• Medium

  Group Anagrams

  Given an array of strings strs, group the anagrams together. You can …

• Medium

  Product of Array Except Self

  Given an integer array nums, return an array answer such that answer[i] …

• Medium

  Rotate Image

  You are given an n x n 2D matrix representing an image, …

  Matrix
• Medium

  Spiral Matrix

  Given an m x n matrix, return all elements of the matrix …

  Matrix Simulation
• Medium

  Set Matrix Zeroes

  Given an m x n integer matrix, if an element is 0, …

  Matrix
• Medium

  Min Stack

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

  Stack
• Medium

  Daily Temperatures

  Given an array of integers temperatures represents the daily temperatures, return an …

  Stack
• Medium

  Minimum Size Subarray Sum

  Given an array of positive integers nums and a positive integer target, …

  Sliding Window
• Medium

  Jump Game

  You are given an integer array nums. You are initially positioned at …

  Greedy
• Medium

  Best Time to Buy and Sell Stock II

  You are given an integer array prices where prices[i] is the price …

  Greedy
• Medium

  Subsets

  Given an integer array nums of unique elements, return all possible subsets …

  Backtracking Bit Manipulation
• Medium

  Permutations

  Given an array nums of distinct integers, return all the possible permutations. …

  Backtracking
• Medium

  Combination Sum

  Given an array of distinct integers candidates and a target integer target, …

  Backtracking
• Medium

  House Robber

  You are a professional robber planning to rob houses along a street. …

• Medium

  Coin Change

  You are given an integer array coins representing coins of different denominations …

• Medium

  Unique Paths

  There is a robot on an m x n grid. The robot …

  Math
• Medium

  Sort Colors

  Given an array nums with n objects colored red, white, or blue, …

  Sorting
• Medium

  Kth Largest Element in an Array

  Given an integer array nums and an integer k, return the k-th …

  Arrays Divide and Conquer Sorting
• Hard

  Merge k Sorted Lists

  You are given an array of k linked-lists lists, each linked-list is …

• Hard

  Trapping Rain Water

  Given n non-negative integers representing an elevation map where the width of …

• Hard

  Longest Valid Parentheses

  Given a string containing just the characters '(' and ')', return the …