ZOJ 3791 An easy game DP+组合数

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#define LL long long
using namespace std;
LL dp[110][110];
LL c[110][110];
int n,m,k,len;
char s1[110],s2[110];
const LL M=1000000000+9;
void init()
{
    c[0][0]=1;
    for (int i=1;i<110;i++){
        c[i][0]=1;
        for (int j=1;j<=i;j++){
            c[i][j]=c[i-1][j-1]+c[i-1][j];
            c[i][j]%=M;
        }
    }
}
int main()
{
    init();
    while (scanf("%d%d%d",&n,&k,&m)!=EOF)
    {
        scanf("%s%s",s1,s2);
        int a=0;
        for (int i=0;i<n;i++){
            if (s1[i]!=s2[i]){
                a++;
            }
        }
        memset(dp,0,sizeof dp);
        dp[0][a]=1;
        for (int i=0;i<k;i++){
            for (int j=0;j<=n;j++){
                if (dp[i][j]){
                    for (int q=0;q<=min(m,j);q++){
                        int sta=j+m-2*q;
                        dp[i+1][sta]+=c[j][q]*c[n-j][m-q]%M*dp[i][j]%M;
                        if (dp[i+1][sta]>=M) dp[i+1][sta]%=M;
                    }
                }
            }
        }
        printf("%lld\n",dp[k][0]);
    }
    return 0;
}