374. 猜数字大小
猜数字游戏的规则如下:
每轮游戏,我都会从 1 到 n 随机选择一个数字。 请你猜选出的是哪个数字。
如果你猜错了,我会告诉你,你猜测的数字比我选出的数字是大了还是小了。
你可以通过调用一个预先定义好的接口 int guess(int num) 来获取猜测结果,返回值一共有 3 种可能的情况(-1,1 或 0):
-1:我选出的数字比你猜的数字小 pick < num
1:我选出的数字比你猜的数字大 pick > num
0:我选出的数字和你猜的数字一样。恭喜!你猜对了!pick == num
返回我选出的数字。
二分
1.向上取整
/**
* Forward declaration of guess API.
* @param num your guess
* @return -1 if num is higher than the picked number
* 1 if num is lower than the picked number
* otherwise return 0
* int guess(int num);
*/
class Solution {
public:
int guessNumber(int n) {
long long l=1,r=n;
while(l<r){
long long mid=(l+r)>>1;
if(guess(mid)==0)return mid;
else if(guess(mid)==1)l=mid+1;
else r=mid;
}
return r;
}
};
2.向下取整
/**
* Forward declaration of guess API.
* @param num your guess
* @return -1 if num is higher than the picked number
* 1 if num is lower than the picked number
* otherwise return 0
* int guess(int num);
*/
class Solution {
public:
int guessNumber(int n) {
long long l=1,r=n;
while(l<r){
long long mid=(l+r+1)>>1;
if(guess(mid)==0)return mid;
else if(guess(mid)==1)l=mid;
else r=mid-1;
}
return r;
}
};
标签:guess,return,数字,int,mid,num,大小,374
From: https://www.cnblogs.com/isomer/p/17913777.html