Problem Library

Given an array of integers nums and an integer target, return indices of the two numbers such that they add…

Given a string s containing just the characters (, ), {, }, [ and ], determine if the input string is valid.

Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number…

Given an integer array nums, find the subarray with the largest sum, and return its sum.

You are given an array prices where prices[i] is the price of a given stock on the ith day.

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

Given the head of a singly linked list, reverse the list, and return the reversed list.

Design a data structure that follows the constraints of a Least Recently Used (LRU) cache.

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

Given an integer array nums, return true if any value appears at least twice in the array, and return false…

You are given the heads of two sorted linked lists list1 and list2.

Given two strings s and t, return true if t is an anagram of s, and false otherwise.

Given head, the head of a linked list, determine if the linked list has a cycle in it.

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all…

Given an array of integers nums which is sorted in ascending order, and an integer target, write a function…

Given the root of a binary tree, invert the tree, and return its root.

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M, corresponding to values 1…

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

Given a string s, find the length of the longest substring without repeating characters.

Given an array of strings strs, group the anagrams together. You can return the answer in any order.

Given the root of a binary tree, return the level order traversal of its nodes' values (i.e., from left to…

Given the root of a binary tree, return its maximum depth.

Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return…

Write a function that reverses a string. The input string is given as an array of characters s.

Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the…

You are given a large integer represented as an integer array digits, where each digits[i] is the i-th digit…

Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k…

Write an algorithm to determine if a number n is happy.

Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer…

Given an integer array nums and an integer k, return the kth largest element in the array.

There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an…

Given two strings ransomNote and magazine, return true if ransomNote can be constructed by using the letters…

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money…

Given an array nums of size n, return the majority element.

Given an integer n, return a string array answer (1-indexed) where: - answer[i] == "FizzBuzz" if i is…

Given the roots of two binary trees p and q, write a function to check if they are the same or not.

Given an integer x, return true if x is a palindrome, and false otherwise.

Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).

Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range…

Given a string s and a dictionary of strings wordDict, return true if s can be segmented into a…

You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest…

Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.

Given an integer array nums of unique elements, return all possible subsets (the power set).

Given an array of distinct integers candidates and a target integer target, return a list of all unique…

You are given an m x n grid where each cell can have one of three values: - 0 representing an empty cell, - 1…

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in…

You are given an integer array height of length n. There are n vertical lines drawn such that the two…

Given the root of a binary tree, return the length of the diameter of the tree.

Given the root of a binary tree, determine if it is a valid binary search tree (BST).

Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST.

Given the root of a binary tree, imagine yourself standing on the right side of it, return the values of the…

Given an integer array nums, move all 0s to the end of it while maintaining the relative order of the…

Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each…

Given two strings s and p, return an array of all the start indices of p's anagrams in s. You may return the…

You are given an integer array nums. You are initially positioned at the array's first index, and each…

There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0])…

A message containing letters from A-Z can be encoded into numbers using the mapping: 'A' → "1", 'B' → "2"…

Given an integer array nums, find a subarray that has the largest product, and return the product.

Given a string s, return the longest palindromic substring in s.

Given an integer array nums, return the length of the longest strictly increasing subsequence.