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How to Install and Run Local TURN Server on AWS for WebRTC

Traversal Using Relays around NAT (TURN) is a protocol that assists in traversal of network address translators (NAT) or firewalls for multimedia applications. For most WebRTC applications to function a server is required for relaying the traffic between peers, since a direct socket is often not possible between the clients . . . Read more

Longest Common Prefix

Problem Statement Write a function to find the longest common prefix string amongst an array of strings. If there is no common prefix, return an empty string “”. Examples Solution

Valid Parentheses

Problem Statement Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Note that an empty string is also considered valid. . . . Read more

Count Directories

Problem Statement Given a directory change command cd a/b/../c/d/e/../../ output the visit count of each directory such as: {a=2, b=1, c=2, d=2, e=1}. Solution

Balls and Bins

Problem Statement Given m balls and n bin, find out how many ways exist to assign the balls to then bins. Note: the buckets have no order. That is, (1,2,3) and (3,2,1) are considered the same. Example Solution This can be solved using dynamic programming. The solution builds up upon . . . Read more

Shortest Path in Directed Acyclic Graph

Problem Statement Given a weighted Directed Acyclic Graphs (DAG), find the shortest path to a particular point from the given starting point. One thing you can do is apply an O(N*N) algorithm and find the shortest distance by calculating all the distances from each node to every other node. As . . . Read more

Coin in Line

Problem Statement A and B are playing a game. At the beginning there are n coins. Given two more numbers x and y. In each move a player can pick x or y or 1 coins. A always starts the game. The player who picks the last coin wins the game. For . . . Read more

Replace And Remove

Problem Statement Consider the following two rules that are to be applied to strings over the alphabets: [‘a’, ‘b’, ‘c’, ‘d’] Replace each ‘a’ with ‘dd’ Delete each ‘b’ Solution

Out of Boundary Paths

Problem Statement There is an m by n grid with a ball. Given the start coordinate (i,j) of the ball, you can move the ball to adjacent cell or cross the grid boundary in four directions (up, down, left, right). However, you can at most move N times. Find out . . . Read more

Unique Paths II

Problem Statement A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ . . . Read more