bzoj2052: Pku1777 Vivian

题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=2052

2052: Pku1777 Vivian

Time Limit: 10 Sec Memory Limit: 256 MB
Submit: 28 Solved: 14
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Description

Input

Output

Sample Input

Sample Output

HINT

Source

梅森素数。。。

没写这道题之前根本不知道梅森素数。。。好像如果f(n)=sigma(d|n,d)=2^k，n一定是不重复的梅森素数之积，且k=梅森指数之和。。。

具体看这篇吧：http://blog.csdn.net/acm_cxlove/article/details/7860735

代码：

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 using namespace std;
 5 int k,cnt,pp[8]={2,3,5,7,13,17,19,31},sum[256],ans;
 6 long long p[8]={3,7,31,127,8191,131071,524287,2147483647};
 7 bool v[256];
 8 int calc(int x){
 9     int y=0;
10     for(int i=0;i<8;i++)
11     if(x%p[i]==0){
12         x/=p[i];y=y+(1<<i);
13     }
14     if(x!=1)return -1;
15     return y;
16 }
17 int main(){
18     //freopen("data.in","r",stdin);
19     //freopen("data.out","w",stdout);
20     for(int i=0;i<256;i++)
21     for(int j=0;j<8;j++)
22     if(i&(1<<j))sum[i]+=pp[j];
23     while(~scanf("%d",&k)){
24         memset(v,0,sizeof(v));v[0]=1;
25         for(int i=1;i<=k;i++){
26             int x;scanf("%d",&x);
27             x=calc(x);
28             if(x==-1)continue;
29             for(int j=255;j;j--)
30             if((j&x)==x&&v[j^x])v[j]=1;
31         }
32         ans=0;
33         for(int i=0;i<256;i++)
34         if(v[i]&&sum[i]>ans)ans=sum[i];
35         if(ans)printf("%d
",ans);
36         else printf("NO
");
37     }
38     return 0;
39 }

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