Guess Number Higher or Lower

原创于 2016-09-02 17:28:19 发布 · 256 阅读

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#leetcode #二分查找

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本文介绍了一种使用二分查找法解决猜数字游戏问题的方法。通过预定义的API反馈，不断缩小猜测范围直至找到正确答案。

题目描述：

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.

其实我觉得这个题难在读懂提，读懂题就好说了，用二分法搞定

public class Solution extends GuessGame {
    public int guessNumber(int n)   
    {  
        if(guess(n) == 0)  
           return n;  
        int left = 1;  
        int right = n;  
        while(left < right)  
        {  
            int mid = left + (right - left)/2;  
            if(guess(mid) == 0)  
               return mid;  
            else if(guess(mid) == -1)  
               right = mid - 1;  
            else if(guess(mid) > 0)  
               left = mid + 1;  
        }  
        return left;  
    }  
}