Some of my favorite answers:

What are the differences between NP, NP-Complete and NP-Hard?

Why do we need boxing and unboxing in C#?

Can anyone explain this algorithm for calculating large factorials?

What is memoization and how can I use it in Python?

Primitive cast and assignments in Java

mapreduce - how to anonymize a column's values

How does Java know where to jump to when breaking out of a loop?