Codeforces621E 矩阵构造快速幂

比赛的时候 构造矩阵想岔了，矩阵构造熟练度明显不够。。。

ACCode：

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<sstream>
#include<string>
#include<bitset>
using namespace std;

typedef long long LL;

const LL LINF = (1LL <<63);
const int INF = 1 << 31;


const int NS = 100010;
const int MS = 10;
const int KS = 105;
const LL MOD = 1000000007;

struct matrix{
    #define M_SIZE (KS)
    int len;
    int a[M_SIZE][M_SIZE];

    void initClear(int _len)
    {
        len = _len;
        memset(a, 0, sizeof(a));
    }

    void initOne(int _len)
    {
        initClear(_len);
        for(int i = 0; i < len; i++)
        {
            a[i][i] = 1;
        }
    }

    void initStruct(int _len, int* dig)
    {
        initClear(_len);

        int lim = min(MS, len);
        for(int i = 0; i < len; i++)
        {
            for(int j = 0; j < lim; j++)
            {
                int vi = (i * 10 + j) % len;
                a[i][vi] += dig[j];
            }
        }
    }

    matrix operator * (const matrix &right)const
    {
        matrix res; res.initClear(len);

        for(int row = 0; row < len; row++)
        {
            for(int col = 0; col < len; col++)
            {
                for(int pos = 0; pos < len; pos++)
                {
                    if(a[row][pos] > 0 && right.a[pos][col])
                    {
                        res.a[row][col] += ((LL)a[row][pos] * right.a[pos][col]) % MOD;
                        if(res.a[row][col] >= MOD)
                        {
                            res.a[row][col] -= MOD;
                        }
                    }
                }
            }
        }

        return res;
    }

    matrix operator + (const matrix &right)const
    {
        matrix res; res.initClear(len);

        for(int row = 0; row < len; row++)
        {
            for(int col = 0; col < len; col++)
            {
                res.a[row][col] = (this->a[row][col] + right.a[row][col]);
                if(res.a[row][col] >= MOD)
                {
                    res.a[row][col] -= MOD;
                }
                else if(res.a[row][col] < 0)
                {
                    res.a[row][col] += MOD;
                }
            }
        }
        return res;
    }

    matrix qpow(LL y)
    {
        matrix ans; ans.initOne(this->len);
        matrix x; x = *this;
        for(;y > 0; y >>= 1)
        {
            if(y & 1)
            {
                ans = ans * x;
            }
            x = x * x;
        }
        return ans;
    }

    void print()
    {

        for(int row = 0; row < len; row++)
        {
            for(int col = 0; col < len; col++)
            {
                cout<<this->a[row][col]<<" ";
            }
            puts("");
        }
        puts("");
    }
};

int n, b, k, x;
int dig[MS];
matrix mat;

int main()
{
#ifndef ONLINE_JUDGE
    freopen("621E.in", "r", stdin);
//    freopen("out.txt", "w", stdout);
#endif
    while(~scanf("%d %d %d %d", &n, &b, &k, &x))
    {
        int d;
        memset(dig, 0, sizeof(dig));
        for(int i = 0; i < n; i++)
        {
            scanf("%d", &d);
            dig[d]++;
        }
        if(x < MS)
        {
            for(int i = x; i < MS; i++)
            {
                dig[i % x] += dig[i];
                dig[i] = 0;
            }
        }

        mat.initStruct(x, dig);
//        mat.print();
//        printf("-------------\n");
        mat = mat.qpow(b);
//        mat.print();
//        printf("-------------\n");
        printf("%d\n", mat.a[0][k]);
    }
    return 0;
}