Problem

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

Input: 16
Output: true

Input: 14
Output: false

Code

static int var = [](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    bool isPerfectSquare(int num) {
        long temp = num;
        while (temp*temp > num)
            temp = (temp + num/temp) / 2;
        return temp*temp == num;
    }
};

Result

image.png