class Solution {public:    int sqrt(int x) {        long long left = 0;        long long right = x/2 + 1;                while(left <= right)        {            long long tmp = (left + right)/2 * ((left + right)/2); // 一定要注意括号，后面的括号要是少了就错了，因为会先乘再除2结果就不一样            if (tmp == x) return (left + right)/2;            else if (tmp > x)                right = (left+right)/2 - 1;            else                left = (left+right)/2 + 1;        }        return right;    }};