Given a positive integer num, write a function which returns True if num is a perfect square else False.
Follow up: Do not use any built-in library function such as sqrt.
Example 1:
Input: num = 16 Output: true
Example 2:
Input: num = 14 Output: false
Constraints:
1 <= num <= 2^31 - 1
[Math] [Binary Search]
- Sqrt(x) (Easy)
- Sum of Square Numbers (Medium)