非空子集个数

A - A

Time Limit:1000MS     Memory Limit:131072KB     64bit IO Format:%I64d & %I64u

Submit Status

Description

soda has a set  with  integers . 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  are key set.

 

Input

There are multiple test cases. The first line of input contains an integer  , indicating the number of test cases. For each test case: 

The first line contains an integer  , the number of integers in the set.

 

Output

For each test case, output the number of key sets modulo 1000000007.

 

Sample Input

41234 

 

Sample Output

013
7 
首先要理解题意，注意细节，这道题的意思是一个集合S中有n个整数，求元素个数为偶数的非空子集有多少个，知道公式2^(n-1)(mod)-1;就很简单了
记得是要对1000000007取模！！
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#include<stdio.h>__int64 f(__int64 a,__int64 b,__int64 c){__int64 t=1;a=a%c;while(b>0){if(b%2==1)t=t*a%c;b=b/2;a=a*a%c;}return t;}int main(){int t;__int64 n;scanf("%d",&t);while(t--){scanf("%I64d",&n);printf("%I64d\n",f(2,n-1,1000000007)-1);}return 0;}