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

Solution:

public class Solution {
    public boolean isPerfectSquare(int num) {
        long x = num;
        while(x*x>num){
            x = (x+num/x)/2;
        }
        return x*x==num;
    }
}