hdu 1757 A Simple Math Problem

http://acm.hdu.edu.cn/showproblem.php?pid=1757

　　如题，简单的矩阵快速幂。1y！

#include <cstdio>
#include <cstring>
#include <cassert>
#include <algorithm>

using namespace std;

const int maxSize = 10;
const int initMod = 1E9 + 7;
int curSize = maxSize;
int curMod = initMod;

struct Matrix {
    int val[maxSize][maxSize];

    Matrix(bool ONE = false) {
        for (int i = 0; i < curSize; i++) {
            for (int j = 0; j < curSize; j++) {
                val[i][j] = 0;
            }
            if (ONE) val[i][i] = 1;
        }
    }

    void print(int _l = curSize, int _w = curSize) {
        for (int i = 0; i < _l; i++) {
            for (int j = 0; j < _w; j++) {
                if (j) putchar(' ');
                printf("%d", val[i][j]);
            }
            puts("");
        }
        puts("~~");
    }
};

Matrix operator * (Matrix &_a, Matrix &_b) {
    Matrix ret = Matrix();

    for (int i = 0; i < curSize; i++) {
        for (int k = 0; k < curSize; k++) {
            if (_a.val[i][k]) {
                for (int j = 0; j < curSize; j++) {
                    ret.val[i][j] += _a.val[i][k] * _b.val[k][j];
                    ret.val[i][j] %= curMod;
                }
            }
        }
    }

    return ret;
}

Matrix operator ^ (Matrix &_a, int _p) {
    Matrix __a = _a, ret = Matrix(true);

    while (_p) {
        if (_p & 1) {
            ret = ret * __a;
        }
        __a = __a * __a;
        _p >>= 1;
    }

    return ret;
}

int deal(int k) {
    if (k < 10) return k % curMod;

    Matrix ans = Matrix(), op = Matrix();

    for (int i = 0; i < 10; i++) {
        ans.val[0][i] = 9 - i;
    }
//    ans.print();
    for (int i = 0; i < 10; i++) {
        scanf("%d", &op.val[i][0]);
    }
    for (int i = 1; i < 10; i++) {
        op.val[i - 1][i] = 1;
    }
//    op.print();
    op = op ^ (k - 9);
    ans = ans * op;
//    ans.print();

    return ans.val[0][0];
}

int main() {
    int n;

    while (~scanf("%d%d", &n, &curMod)) {
        printf("%d\n", deal(n));
    }

    return 0;
}

——written by Lyon