Leetcode--Add to List 374. Guess Number Higher or Lower

题目

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.
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!
Example:
n = 10, I pick 6.
Return 6.

思路

二分法，注意求mid时用low + (high - low) / 2;，否则可能会出现溢出

代码

class Solution {public:    int guessNumber(int n) {        int low = 1;        int high = n;        int res;        int mid;        while(high > low) {            mid = low + (high - low) / 2;            res = guess(mid);            if(res == 1) low = mid + 1;            else if(res == -1) high = mid - 1;            else return mid;        }        return low;    }};