374. Guess Number Higher or Lower Easy

这道题是二分查找的使用。需要注意的是，求mid不可以用（right + left）/ 2，因为可能会越界，超过int的最大值，应该用（right - left）/ 2 + left。

// Forward declaration of guess API.// @param num, your guess// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0int guess(int num);class Solution {public:    int guessNumber(int n) {        int left = 1, right = n;        while(left <= right){            int mid = (right - left) / 2 + left;            int d = guess(mid);            if(d == -1)right = mid - 1;            else if(d == 1)left = mid + 1;            else return mid;        }    }};