Guess Number Higher or Lower

description

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.

thinking

这道题是一道典型的猜价格的问题，根据对方说高了还是低了来缩小范围，最简单快速的方法就是折半搜索法

solution

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