Perfect Squares

A perfect square is an integer that equals some integer squared. For example, $16 = 4^2$, so 16 is a perfect square. But 15 is not because $\sqrt{15}$ is not an integer.

You can check if $n$ is a perfect square by computing $\sqrt{n}$ and checking if it's an integer. In code: take the floor of the square root, square it, and see if you get $n$ back.

Perfect squares appear in number theory problems, geometry (area calculations), and dynamic programming. Let me show you a problem that uses this concept.