LeetCode 374 Guess Number Higher or Lower

LeetCode 374 Guess Number Higher or Lower

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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.

这道题略坑，my number指的是最后的正确答案，而不是你猜测的值。同时在二分搜索的时候要注意，mid可以有两种计算方法，但第一种由于low + high超出int范围而超时。

mid = (low + high) / 2; 
mid = low + (high - low) / 2;

代码如下：

    public int guessNumber(int n) {
        int low = 1, high = n;
        while (low < high) {
            int mid = low + (high - low)/2;
            int cmp = guess(mid);
            if (cmp == 0) return mid;
            else if (cmp == 1) {
                low = mid + 1;
            } else {
                high = mid - 1;
            }
        }
        return low;
    }