69 x的平方根

class Solution {
    public:
        int mySqrt(int x) {
            if (x == 0) {
                return 0;
            }
            

            for(int i=1;i<=x;i++){
                if((long long)i*i<=x&&(long long)(i+1)*(i+1)>x){
                    return i;
                }
            }
            return 0;
        }
};

直接暴力解，注意i*i可能会超出int范围，转为long long