组队 (Teams,UVa 11609)

 1 #include <iostream>
 2 #include <string.h>
 3 #include <string>
 4 #include <fstream>
 5 #include <algorithm>
 6 #include <stdio.h>
 7 #include <vector>
 8 #include <queue>
 9 #include <set>
10 #include <cmath>
11 using namespace std;
12 const double eps = 1e-8;
13 const int INF=0x7fffffff;
14 unsigned long long uINF = ~0LL;
15 #define MAXN 10000007
16 typedef long long LL;
17 LL vis[MAXN];
18 LL prime[MAXN];
19 
20 void sieve(LL n)
21 {
22     LL m=(LL)sqrt(n+0.5);
23     memset(vis,0,sizeof(vis));
24     for(LL i=2;i<=m;i++)if(!vis[i])
25     for(LL j=i*i;j<=n;j+=i)vis[j]=1;
26 }
27 
28 LL gen_prime(LL n)
29 {
30     sieve(n);
31     LL c=0;
32     for(LL i=2;i<=n;i++)if(!vis[i])
33         prime[c++]=i;
34     return c;
35 }
36 
37 LL gcd(LL a,LL b)
38 {
39     return b==0?a:gcd(b,a%b);
40 }
41 
42 LL pow_mod(LL a,LL n,LL m)
43 {
44     if(n==0)return 1;
45     LL x=pow_mod(a,n/2,m);
46     LL ans=x*x%m;
47     if(n%2==1)ans=ans*a%m;
48     return ans;
49 }
50 
51 int main()
52 {
53     int T,t=1;
54     scanf("%d",&T);
55     LL n;
56     while(T--)
57     {
58         scanf("%lld",&n);
59         LL ans=pow_mod(2,n-1,1000000007);
60         ans=ans*n%1000000007;
61         printf("Case #%d: %lld
",t++,ans);
62     }
63 
64     return 0;
65 }
ans=n* 2^(n-1);