Practice - Sum of Square Numbers

Given a non-negative integer $c$, decide whether there exist two integers $a$ and $b$ such that $a^2 + b^2 = c$.

For example, $c = 5$ returns true because $1^2 + 2^2 = 1 + 4 = 5$. But $c = 3$ returns false.

Hint: use two pointers starting at $a = 0$ and $b = \lfloor \sqrt{c} \rfloor$. Move pointers based on whether $a^2 + b^2$ is less than, equal to, or greater than $c$.