guess number higher or lower

文章目录

1. 1. 题意介绍
2. 2. 代码区

题意介绍

---

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.

比较简单的题，用二分解决，但是有一个细节，导致多次才ac。
将lower+(higher-lower)/2写成(lower＋higher)/2,两个结果应该相同，但是会报错，timelimited
，大数出错，应该是溢出，用后一个公式可以有效减少上限

代码区

---

int guess(int num);
class Solution {
public:
    int guessNumber(int n) {
        if(guess(n)==0)
            return n;
        int lower = 1;
        int higher = n;
        while(lower<higher){
            int temp = lower+(higher-lower)/2;
            int t = guess(temp);
            if(t==0)
            {
                return temp;
            }
            if(t==1)
                lower = temp;
            else
                higher = temp;
        }
        return lower;
    }
};