Key Set
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 362 Accepted Submission(s): 238
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
Source
2015 Multi-University Training Contest 6
题目链接:点击打开链接
#include<cstdio> #include<cstring> #include<algorithm> #include<iostream> using namespace std; __int64 f( __int64 n,__int64 m,__int64 s) { __int64 t; n=n%s; t=1; if(n==0)return 0; while(m) { if(m%2==1) { t*=n; t%=s; } n*=n; n%=s; m/=2; } return t; } int main() { __int64 n,i,x; scanf("%I64d",&n); for(i=1;i<=n;i++) { scanf("%I64d",&x); if(x==1) { printf("0\n"); continue; } __int64 t=f(2,x-1,1000000007); printf("%I64d\n",t-1); } }
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