【循环数组】#51 A. Flea travel

A. Flea travel

time limit per test

2 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

A flea is sitting at one of the n hassocks, arranged in a circle, at the moment. After minute number k the flea jumps through k - 1 hassoсks (clockwise). For example, after the first minute the flea jumps to the neighboring hassock. You should answer: will the flea visit all the hassocks or not. We assume that flea has infinitely much time for this jumping.

Input

The only line contains single integer: 1 ≤ n ≤ 1000 — number of hassocks.

Output

Output "YES" if all the hassocks will be visited and "NO" otherwise.

Sample test(s)

input

1

output

YES

input

3

output

NO

枚举题意和调试累死我了……Q^Q 居然memset和init写反了……

有一个跳蚤在一圈草丛中的一个，顺时针跳，第1分钟跳1个，第二分钟俩，第三分钟仨~

问这么无限下去能不能有朝一日给它遍历完。

其实不是无限啦~ 既然是一圈的话，跳N个不就是跳N-N%n个嘛~

那么我们记录每一个草丛第一次经过的时候跳跃力mod(n)是step，下一次又用这个跳跃力mod(n)到达这里之后不就是无限循环了嘛~

Code:

#include <cstdio>#include <memory>#include <cstring>#include <iostream>#include <algorithm>using namespace std;int main(){int n;cin>>n;if(n==1){cout<<"YES"<<endl;return 0;}int steps=0,mrk[1001];int now=0,cnt=0,flag=0,step=0;memset(mrk,-1,sizeof mrk);mrk[0]=0,cnt=1,step=0,now=0;while(1){if(cnt==n){flag=1;break;}step= (step+1)%n;now= (now+step)%n;if(mrk[now]==step)break;if(mrk[now]==-1){cnt++;mrk[now]=step;}//cout<<now<<":"<<mrk[now]<<"  "<<cnt<<endl;} if(flag)cout<<"YES"<<endl;else cout<<"NO"<<endl;return 0;}