367. Valid Perfect Square

题目

Given a positive integer num, write a function which returns True if num is a perfect square else False.

Note: Do not use any built-in library function such as sqrt.

Example 1:

Input: 16
Returns: True

Example 2:

Input: 14
Returns: False

Credits:Special thanks to @elmirap for adding this problem and creating all test cases.

解题思路

见程序注释