Valid Perfect Square

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

 1 public class Solution {
 2     public boolean isPerfectSquare(int num) {
 3         int low = 1, high = num;
 4         
 5         while (low <= high) {
 6             int mid = low + (high - low) / 2;
 7             
 8             if (mid == num / mid && num % mid == 0) return true;
 9             else if (mid > num / mid) high = mid - 1;
10             else low = mid + 1;
11         }
12         return false;
13     }
14 }