Shuffles and Even Splits

Randomness and fair division come up in CrowdStrike coding rounds now and then, mostly at the senior level. The code is only a few lines. Most of your time goes on the argument, where you show that every outcome is equally likely, or that no bucket ends up two items heavier than another.

Random code is hard to test, so say how you'd check it. Run it many times and count each outcome against its expected share, and seed the generator so a failing run repeats. Also know which random source you'd ship. CrowdStrike sells security, and a shuffle or token an attacker can predict is a vulnerability there. A seeded Mersenne Twister gives its state away after enough output, so it's fine for tests but not for anything that guards a system. For that, read from the operating system's secure random source. Three problems follow. Start with the shuffle, since a later one reuses it.

CrowdStrikePremium lesson · Coding round

The 3 CrowdStrike problems are below.

1. 1A Premium questionCoding · Medium
2. 2A Premium questionCoding · Easy
3. 3A Premium questionCoding · Medium

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