[LeetCode] Sqrt(x)

Implement int sqrt(int x).
It can be solved through Newton's method.

Compute and return the square root of x.

class Solution {
public:
    int sqrt(int x) {
    if (x == 0) return 0;
    double last = 0;
    double res = 1;
    while (res != last)
    {
        last = res;
        res = (res + x / res) / 2;
    }
    return int(res);
}
};