// Valid Perfect Square — EASY

// Category: binary-search

Given a positive integer `num`, return `true` if `num` is a perfect square, or `false` otherwise.

A **perfect square** is an integer that is the square of an integer. In other words, it is the product of some integer with itself.

You must not use any built-in library function, such as `sqrt`.

Example: num = 16

Output: true