[LeetCode]--374. Guess Number Higher or Lower

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.

思路就是二分查找法。

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