【leetcode73】经典算法-Guess Number Higher or Lower

题目描述：

从1～n中，随便的拿出一个数字，你来猜测。

提示

提供一个guess(int num)的api，针对猜测的数字，返回三个数值。0，-1,1

0;猜中返回num

-1：比猜测的数值小

1：比猜测的数值大

例如：

n = 10, I pick 6.

Return 6.

原文描述：

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.

思路分析：

明显是二分法的应用，关于二分法，看我之前的一片博客，讲的比较详细，链接如下：
Java语言实现二分法

代码：

/* 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 = 1,R = n;
while(L <= R){
int mid = L + ((R - L) >> 1);
int res = guess(mid);
if(res == 0) return mid;
else if(res == 1)  L = mid + 1;
else R = mid - 1;
}
return L;
}
}

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leetcode专栏

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