Key Set
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 362 Accepted Submission(s): 238
Problem Description
S with n integers {1,2,…,n}. A set is called key set if the sum of integers in the set is an even number. He wants to know how many nonempty subsets of S
Input
T
(1≤T≤105), indicating the number of test cases. For each test case:
The first line contains an integer
n
(1≤n≤109), the number of integers in the set.
Output
For each test case, output the number of key sets modulo 1000000007.
Sample Input
4 1 2 3 4
Sample Output
0 1 3 7
Source
2015 Multi-University Training Contest 6
题目链接: 点击打开链接
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
__int64 f( __int64 n,__int64 m,__int64 s)
{
__int64 t;
n=n%s;
t=1;
if(n==0)return 0;
while(m)
{
if(m%2==1)
{
t*=n;
t%=s;
}
n*=n;
n%=s;
m/=2;
}
return t;
}
int main()
{
__int64 n,i,x;
scanf("%I64d",&n);
for(i=1;i<=n;i++)
{
scanf("%I64d",&x);
if(x==1)
{
printf("0\n");
continue;
}
__int64 t=f(2,x-1,1000000007);
printf("%I64d\n",t-1);
}
}