Valid Perfect Square

{1} Valid Perfect Square
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 1:

Input: num = 16
Output: true
Explanation: We return true because 4 * 4 = 16 and 4 is an integer.
Example 2:

Input: num = 14
Output: false
Explanation: We return false because 3.742 * 3.742 = 14 and 3.742 is not an integer.

class Solution {
    public boolean isPerfectSquare(int num) {
        long s=1,e=num;
        while(s<=e)
        {
            long mid=s+(e-s)/2;
            if(mid*mid==num)
                return true;
            else if(mid*mid>num)
             e=mid-1;
            else
                s=mid+1;
        }
        return false;

    }
}