hihocoder #1143 : 骨牌覆盖问题·一

http://hihocoder.com/problemset/problem/1143 

斐波那契数列，快速矩阵幂解法

#include <cstdio>
#include <cstring>
#include <vector>

using namespace std;
const int N = 19999997;

void copy(long long a[2][2],long long b[2][2])
{
    for(int i = 0; i < 2; i++)
        for(int j = 0; j < 2; j++)
            a[i][j] = b[i][j];

}

void calc(long long a[2][2],long long b[2][2])
{
    long long c[2][2]={0};
    c[0][0] = (a[0][0]*b[0][0]+a[0][1]*b[1][0])%N;
    c[0][1] = (a[0][0]*b[0][1]+a[0][1]*b[1][1])%N;
    c[1][0] = (a[1][0]*b[0][0]+a[1][1]*b[1][0])%N;
    c[1][1] = (a[1][0]*b[0][1]+a[1][1]*b[1][1])%N;
    copy(a,c);
}

int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        long long c[2][2]={0,1,1,1};
        long long res[2] = {1,1};
        int flag = 0;
        for(int k = 0; (1<<k) <= n;k++)
        {
            if(n & (1<<k))
            {
                long long u = (res[0]*c[0][0]+res[1]*c[0][1])%N;
                long long v = (res[0]*c[1][0]+res[1]*c[1][1])%N;
                res[0] = u;
                res[1] = v;
            }
            calc(c,c);
        }
        printf("%lld\n",res[0]);
    }
    return 0;
}