# Join live collaborative sessions and solve LeetCode problems with peers.

Practice tech interviews with peers, track your progress, receive feedback, and land offers from awesome companies.   ## String Compression

Given an array of characters chars, compress it using the following algorithm: ## Validate Binary Search Tree

Given the root of a binary tree, determine if it is a valid binary search tree (BST). ## Subarray Sum Equals K

Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals... ## Squares of a Sorted Array

Given an integer array nums sorted in non-decreasing order, return an array of the squares of each number sorted in non-decreasing order.... ## Check If N and Its Double Exist

Given an array arr of integers, check if there exist two indices i and j such that : ## Remove Element

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The relative order of the... ## Merge Sorted Array

You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number... 