HDOJ 5363 Key Set

Key Set

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 1870    Accepted Submission(s): 983

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
  
  
  
  


  
  
  
  


  
  
  
  

   
   快速幂和排列组合结合的题，题解有空补上（其实是自己还不清楚）
  
  
  
  

   
   
#include<stdio.h>
#include<string.h>
long long MI(long long a,long long b)
{
	long long ans=1;
	while(b>0)
	{
		if(b%2==1)
		ans=(ans*a)%1000000007;
		b=b/2;
		a=(a*a)%1000000007;
	}
	return ans;
}
int main()
{
	int t;
	long long n;
	scanf("%d",&t);
	while(t--)
	{
		scanf("%lld",&n);
		printf("%lld\n",MI(2,n-1)-1);
	}
}