leetcode-69.cpp

class Solution {
public:
    int mySqrt(int x) {
        int min = 0;
        int max = 46340;
        while (min < max) {
            const int mid = (min + max) >> 1;
            const int s = mid * mid;
            if (s > x) {
                max = mid-1;
            } else if (s < x) {
                min = mid + 1;
            } else {
                return mid;
            }
        }
        if (min*min <= x) {
            return min;
        }
        return min - 1;
    }
};