BZOJ 1801--中国象棋(DP)

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<iostream>
#define N 110
#define LL long long
#define mod 9999973
using namespace std;
inline int Read(){
    int x=0,f=1;char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
    return x*f;
}
int n,m;
LL dp[N][N][N];
int main(){
    LL ans=0;
    n=Read();m=Read();
    dp[0][0][0]=1;
    for(int i=0;i<n;i++){
        for(int j=0;j<=m;j++){
            for(int k=0;k+j<=m;k++){
                if(!dp[i][j][k]) continue;
                dp[i+1][j][k]=(dp[i+1][j][k]+dp[i][j][k])%mod;
                if(k>=2) dp[i+1][j+2][k-2]=(dp[i+1][j+2][k-2]+dp[i][j][k]*(k*(k-1)/2)%mod)%mod;
                if(k>=1 && (m-j-k)>=1 ) dp[i+1][j+1][k]=(dp[i+1][j+1][k]+dp[i][j][k]*k*(m-j-k)%mod)%mod;
                if((m-j-k)>=2) dp[i+1][j][k+2]=(dp[i+1][j][k+2]+dp[i][j][k]*((m-j-k)*(m-j-k-1)/2)%mod)%mod;
                if(k>=1) dp[i+1][j+1][k-1]=(dp[i+1][j+1][k-1]+dp[i][j][k]*k%mod)%mod;
                if((m-j-k)>=1) dp[i+1][j][k+1]=(dp[i+1][j][k+1]+dp[i][j][k]*(m-j-k)%mod)%mod;
            }
        }
    }
    for(int j=0;j<=m;j++)
        for(int k=0;k+j<=m;k++)
            ans=(ans+dp[n][j][k])%mod;
    printf("%lld\n",ans);
    return 0;
}