### Picking a random element from an incoming stream

Here is the problem Good morning! Here's your coding interview problem for today. This problem was asked by Facebook. Given a stream of elements too large to store in memory, pick a random element from the stream with uniform probability. Upgrade to premium and get in-depth solutions to every problem. If you liked this problem, feel free to forward it along so they can subscribe here ! As always, shoot us an email if there's anything we can help with! The key here is to use a simple count and always decide on the following: - If when picking a random number between 0 and count (inclusive) gives you 0, then pick the new element - Otherwise, don't change elements The probability that you will switch elements is always 1/(count+1), which over time will give you a fair and equal probability across all the elements. Code is below and on Github: https://github.com/BorisVasilenko/dailycodingproblem/blob/master/DailyCodingProblem09292018.cs using System;