leetcode Guess Number Higher or Lower 猜大小

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.
  题意：有一猜大小函数，若大，返回1，若小，返回-1，相等返回0。给定一个范围，返回猜中的给定的数。
  思路：二分法

// 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 max = n, min = 1;        while (true) {            int mid = (max - min) / 2 + min;            int res = guess(mid);            if (res == 0) return mid;            else if (res == 1) min = mid + 1;            else max = mid - 1;        }    }};