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

实现一个二分搜索就好了。。

代码

int guessNumber(int n) {
    int start = 1, end = n, mid = (end-start)/2+start;
    int g = guess(mid);
    while(g!=0) {
        if(g==-1) {
            end = mid-1;
        }
        else {
            start = mid+1;
        }
        mid = (end-start)/2+start;
        g = guess(mid);
    }
    return mid;
    
}