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.

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，原理很简单，参见代码如下：

 

// 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) {        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;    }};

 

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