Monte Carlo method, calculating π

This is a pretty neat way to estimate pi. Rust uses this example in its std::rand documentation: <a href="http://doc.rust-lang.org/std/rand/#monte-carlo-estimation-of-π" rel="nofollow">http:&#x2F;&#x2F;doc.rust-lang.org&#x2F;std&#x2F;rand&#x2F;#monte-carlo-estimation-of...</a>

This was an interview Q on my Google interview. hated it (I ended up using Riemann sums)