Key Set

http://acm.hdu.edu.cn/contests/contest_showproblem.php?pid=1011&cid=594

Key Set

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 476    Accepted Submission(s): 251

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

 

直接输出2的n-1次方-1？当然2的10的9次方的次方肯定很大，然而结果只是对其求余与1000000007，所以快速幂，对每次都求余，就不会超出类型啦

 #include <cstdio>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 using namespace std;
 typedef long long LL;
 const LL mod = ;
 LL Pow (LL x, LL y)
 {
     LL ans = ;
     while (y)
     {
         if (y % )
             ans = ans * x % mod;
         x = x * x % mod;
         y /= ;
     }
     return ans;
 }
 int main ()
 {
     LL t, n;
     scanf ("%lld", &t);
     while (t --)
     {
         scanf ("%lld", &n);
         LL ans = Pow (, n-);
         printf ("%lld\n", ans-);
     }
     return ;
 }