[374]Guess Number Higher or Lower

【题目描述】

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.

【解题思路】

二分搜索

【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 low=1;        int high=n;        int mid;        int ans=-1;        while(1){            mid=(high-low)/2+low;            if(guess(mid)==0){                ans=mid;                break;            }            else if(guess(mid)==1){                low=mid+1;            }            else if(guess(mid)==-1){                high=mid-1;            }                    }        return ans;    }};