[Leetcode] 374. Guess Number Higher or Lower 解题报告

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：

最基本的二分查找，一定要闭着眼睛都能写出来^_^。

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 0int guess(int num);class Solution {public:    int guessNumber(int n) {        int left = 1, right = n;        while(left <= right) {            int mid = left + (right - left) / 2;            int ans = guess(mid);            if(ans == 0) {                return mid;            }            else if(ans == 1) {                left = mid + 1;            }            else {                right = mid - 1;            }        }        return left;    }};