LeetCode-374. Guess Number Higher or Lower

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问题：https://leetcode.com/problems/guess-number-higher-or-lower/?tab=Description
We are playing the Guess Game. The game is as follows:
I pick a number from 1 to n. You have to guess which number I picked.
Every time you guess wrong, I’ll tell you whether the number is higher or lower.
我们正在玩猜词游戏。游戏规则如下：
我从号码1到N中选一个数字。你来猜我选的号码。
每一次你猜错了，我会告诉你我的这个数比你当前选的数高或低。
You call a pre-defined API guess(int num) which returns 3 possible results (-1, 1, or 0):
-1 : My number is lower
1 : My number is higher
0 : Congrats! You got it!
你需要调用预先定义的API guess（int num）返回3个可能的结果（- 1，+ 1，或0）：
-1：我的数字是更小
1：我的数字是更大
0：恭喜！你说对啦。

Example: n = 10, I pick 6. Return 6.
例子：n = 10, I pick 6. Return 6.
分析：二分法，只是用guess来判断大小了。但是不知道为什么mid=(left+right)/2会显示时间超出，只能mid=left+(right-left)/2。
C++代码：

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

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