UVA 10518 How Many Calls?

题意：一个递推式第n项%b是多少。

递推式：

构造矩阵：

#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#include<algorithm>
using namespace std;

long long MOD;
long long n;

struct Matrix
{
    long long A[][];
    int R, C;
    Matrix operator*(Matrix b);
};

Matrix X, Y, Z;

Matrix Matrix::operator*(Matrix b)
{
    Matrix c;
    memset(c.A, , sizeof(c.A));
    int i, j, k;
    for (i = ; i <= R; i++)
    for (j = ; j <= b.C; j++)
    for (k = ; k <= C; k++)
        c.A[i][j] = (c.A[i][j] + (A[i][k] * b.A[k][j]) % MOD) % MOD;
    c.R = R; c.C = b.C;
    return c;
}

void init()
{
    memset(X.A, , sizeof X.A);
    memset(Y.A, , sizeof Y.A);
    memset(Z.A, , sizeof Z.A);

    Z.R = ; Z.C = ;
    Z.A[][] = Z.A[][] = Z.A[][] = ;

    X.R = ; X.C = ;
    X.A[][] = ; X.A[][] = ; X.A[][] = ;
    X.A[][] = ; X.A[][] = ; X.A[][] = ;
    X.A[][] = ; X.A[][] = ; X.A[][] = ;

    Y.R =; Y.C = ;
    for (int i = ; i <= ; i++) Y.A[i][i] = ;
}

void work()
{
    while (n)
    {
        if (n %  == ) Y = Y*X;
        n = n >> ;
        X = X*X;
    }
    Z = Z*Y;

    printf("%lld\n", Z.A[][]);
}

int main()
{
    int Case = ;
    while (~scanf("%lld%lld", &n, &MOD))
    {
        if (!n&&!MOD) break;
        init();
        printf("Case %d: %lld %lld ", Case++, n, MOD);
        work();
    }
    return ;
}