hdu 1757【A Simple Math Problem】

矩阵相乘

#include <cstdio>
#include <cstring>

struct matrix
{
    int g[10][10];
}mt;

int kk,m;

matrix multi(matrix a,matrix b)
{
    matrix ans;

    for(int i = 0;i < 10;i ++)
    {
        for(int j = 0;j < 10;j ++)
        {
            int t = 0;
            for(int u = 0;u < 10;u ++)
            {
                t += a.g[i][u] * b.g[u][j];
                t = t % m;
            }
            ans.g[i][j] = t % m;
        }
    }

    return ans;
}

int solve(int k)
{
    matrix temp = mt;
    matrix ans;
    memset(ans.g,0,sizeof(ans.g));
    for(int i = 0;i < 10;i ++)
    {
        ans.g[0][i] = i;
    }

    for(int i = 0;k != 0;i ++)
    {
        if(k & (1 << i))
            ans = multi(ans,temp);
        temp = multi(temp,temp);
        k = k & (~(1 << i) );
    }

    return ans.g[0][9];
}

int main()
{
    while(scanf("%d%d",&kk,&m) == 2)
    {
        memset(mt.g,0,sizeof(mt.g));
        for(int i = 0;i < 10;i ++)
        {
            int a;
            scanf("%d",&a);
            mt.g[9 - i][9] = a;
            if(i < 9)
            mt.g[9 - i][8 - i] = 1;
        }

        if(kk < 10)
        {
            printf("%d\n",kk % m);
            continue;
        }

        printf("%d\n",solve(kk-9)%m);
    }

    return 0;
}