hdu1757矩阵快速幂

这题不错，开始看题目，以为是道水题，花几分钟打了个暴搜，果断runtime error，栈溢出。于是马上找规律，发现可以转换成矩阵乘法和快速幂解决，不过由于审题不清，搞错了a0...a9的顺序，调了老半天才发现。。。。

/*

 * hdu1757/win.cpp

 * Created on: 2012-7-9

 * Author    : ben

 */

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <cmath>

#include <algorithm>

#include <iostream>

#include <queue>

using namespace std;



const int MAX_ORDER = 11;

int MOD;

typedef int typec;

typedef struct MyMatrix {

    int order;

    typec num[MAX_ORDER][MAX_ORDER];

    MyMatrix(int ord) {

        order = ord;

    }

    void init() {

        for (int i = 0; i < order; i++) {

            for (int j = 0; j < order; j++) {

                num[i][j] = 0;

            }

        }

    }

}MyMatrix;



MyMatrix operator*(MyMatrix ma, MyMatrix mb) {

    int ord = ma.order;

    MyMatrix numc(ord);

    numc.init();

    int i, j, k;

    for (i = 0; i < ord; i++) {

        for (j = 0; j < ord; j++) {

            for (k = 0; k < ord; k++) {

                numc.num[i][j] += ma.num[i][k] * mb.num[k][j];

                numc.num[i][j] %= MOD;

            }

        }    }

    return numc;

}



MyMatrix mpow(MyMatrix ma, int x) {

    int ord = ma.order;

    MyMatrix numc(ord);

    numc.init();

    for (int i = 0; i < ord; i++) {

        numc.num[i][i] = 1;

    }

    for (; x; x >>= 1) {

        if (x & 1) {

            numc = numc * ma;

        }

        ma = ma * ma;

    }

    return numc;

}



int main() {

#ifndef ONLINE_JUDGE

    freopen("data.in", "r", stdin);

#endif

    int k;

    MyMatrix matrix(10);

    matrix.init();

    for(int i = 0; i < 9; i++) {

        matrix.num[i + 1][i] = 1;

    }

    while(scanf("%d%d", &k, &MOD) == 2) {

        for(int i = 9; i >= 0; i--) {

            scanf("%d", &matrix.num[i][9]);

        }

        MyMatrix ret = mpow(matrix, k - 9);

        int ans = 0;

        for(int i = 1; i < 10; i++) {

            ans += (i * ret.num[i][9]) % MOD;

            ans %= MOD;

        }

        printf("%d\n", ans);

    }

    return 0;

}