hdu 5363 Key Set

http://acm.hdu.edu.cn/showproblem.php?pid=5363

Key Set

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 549    Accepted Submission(s): 338

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

 

int Pow(int a, int b)
{
int ans = 1;
while(b)
{
if(b % 2 == 1)
ans *= a;
a *= a;
b /= 2;
}
return ans;
}//快数幂，求a的b次幂

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
#define N 500

long long Pow(long long a, long long b, long long c)
{
    long long ans = 1;
    a %= c;
    while(b)
    {
        if(b % 2 == 1)
            ans = (ans * a) % c;
        a = (a * a) % c;
        b /= 2;
    }
    return ans;
}//快数幂，求a的b次幂，c表示对c取余

int main()
{
    int t;
    long long n, num;
    scanf("%d", &t);
    while(t--)
    {
        scanf("%lld", &n);
        num = Pow(2, n - 1, 1000000007);
        printf("%lld
", num - 1);
    }
    return 0;
}