HDU 5363 Key Set(快速幂取模)

Key Set

Problem Description
soda has a set 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 are key set.
 

Input
There are multiple test cases. The first line of input contains an integer 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
 

 

 

#include<cstdio>
using namespace std;

const long long int mod=1000000007;

void quickmod(int a,int b,long long n)
{
    long long res=1,temp=a%n;
    while(b)
    {
        if(b&1)res=(res*temp)%n;
        temp=(temp*temp)%n;
        b>>=1;
    }
    printf("%lld\n",res-1);
}

int main()
{
    int t,n;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        quickmod(2,n-1,mod);
    }
    return 0;
}