MnZn求助，WA on test 29

275307894a @ 2021-01-31 15:07:32

by 275307894a @ 2021-01-31 15:07:46

#include<cstdio>
#define mod 1000000007
using namespace std;
int n,m,k,x,y,z,a[1039][1039];
long long f[3039][3039];
long long ans1,ans2,ans3,ans4;
char _s;
inline long long find(int x,int y,int l,int r){
    register int i,j,ans;
    if(a[x][y])return 0;f[x][y]=1;
    for(i=x;i<=l;i++){
        for(j=y;j<=r;j++)if(!a[i][j])f[i][j]=(f[i][j]+f[i-1][j]+f[i][j-1])%mod; 
    }
    ans=f[l][r];
    for(i=x;i<=l;i++){
        for(j=y;j<=r;j++)f[i][j]=0;
    }
    return ans;
}
int main(){
//  freopen("1.in","r",stdin);
    register int i,j;
    scanf("%d%d",&n,&m);
    for(i=1;i<=n;i++){
        for(j=1;j<=m;j++){
            _s=getchar();
            while(_s!='.'&&_s!='#') _s=getchar();
            a[i][j]=(_s=='.'?0:1);
        }
    }
    ans1=find(1,2,n-1,m);ans2=find(2,1,n,m-1);
    ans3=find(1,2,n,m-1);ans4=find(2,1,n-1,m);//printf("%lld %lld %lld %lld\n",ans1,ans2,ans3,ans4);
    printf("%lld\n",(ans1*ans2%mod-ans3*ans4%mod+mod)%mod);
}

by wgyhm @ 2021-01-31 19:36:36

orz