WEI-CHENG CHEN

說明

不用內建的方式去做開根號

解法：

二分搜，去找最接近的中間值

class Solution {
public:
    int mySqrt(int x) {
        if (x == 0 || x == 1) return x;
        int left = 0, right = x;
        int mid = 0;
        while(left<=right){
            mid = left+(right-left)/2;
            if((long)mid*mid==x) return mid;
            else if((long)mid*mid<x){
                left = mid+1;
            }else{
                right = mid-1;
            }
        }
        return right;

    }
};