LeetCode374 Guess Number Higher or Lower

zhangjun62

于 2019-05-25 16:31:56 发布

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分类专栏： LeetCode 文章标签： LeetCode

本文链接：https://blog.youkuaiyun.com/zhangjun62/article/details/90548396

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博客围绕LeetCode上的猜数字游戏题目展开。题目要求从1到n中猜出所选数字，每次猜错会告知高低。给出了示例及解题代码，通过二分查找算法，不断缩小猜测范围，最终找到目标数字。

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题目：

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 :

Input: n = 10, pick = 6

Output: 6

/* The guess API is defined in the parent class GuessGame.
@param num, your guess
@return -1 if my number is lower, 1 if my number is higher, otherwise return 0
int guess(int num); */

public class Solution extends GuessGame {
public int guessNumber(int n) {
int l = 0;
int r = n;

while(true){
int mid = l + (r - l >> 1);
if(guess(mid) == 0)
return mid;
else if(guess(mid) == -1)
r = mid - 1;
else
l = mid + 1;
}
}
}