ACM PKU 3734 Blocks

题目描述：http://poj.org/problem?id=3734

递推公式：E(t)=(1+t+t^2/2!+......+..)^2*(1+t^2/2!+t^4/4!+..+)^2
                   =e^2t*((e^t+e^-t)/2)^2
                   =1/4(e^4t+2*e^2t)
                   =sigma(1/4*[4^n+2*2^n]*t^n/n!) n=0,1,2,，，

  ==> a(n)=1/4(4^n+2*2^n)

 

#include <iostream>
#include <cstring>
#include <cstdio>
const int M = 10007;
using namespace std;

int solve (int t,int k)  //快速幂；求的是t的k次幂；
{
    int res=1;
    while(k)
    {
        if(k&1)res=(res*t)%M;
        t=t*t%M;   //这里要取余，不取余会wa
        k>>=1;
    }
    return res;
}

int main()
{
    //freopen("in.txt","r",stdin);
    int n,n_case;
    scanf("%d",&n_case);
    while(n_case--)
    {
        scanf("%d",&n);
        int ans = solve(2,n-1);
        ans = ans*(ans+1)%M;
        printf("%d\n",ans);
    }
    return 0;
}