luogu 4147 玉蟾宫 悬线DP

Code: 

#include<bits/stdc++.h>
using namespace std; 
#define setIO(s) freopen(s".in","r",stdin) 
#define maxn 1002
int n,m;  
int mk[maxn][maxn],l[maxn][maxn],r[maxn][maxn],up[maxn][maxn];     
char str[maxn]; 
int main()
{
    // setIO("input");
    scanf("%d%d",&n,&m); 
    for(int i=1;i<=n;++i) 
    {
        for(int j=1;j<=m;++j) 
        {
            scanf("%s",str+1); 
            if(str[1]=='F') mk[i][j]=up[i][j]=1,l[i][j]=r[i][j]=j; 
        } 
    }
    for(int i=1;i<=n;++i) for(int j=2;j<=m;++j) if(mk[i][j]&&mk[i][j-1]) l[i][j]=l[i][j-1];
    for(int i=1;i<=n;++i) for(int j=m-1;j>=1;--j) if(mk[i][j]&&mk[i][j+1]) r[i][j]=r[i][j+1]; 
    int ans=0; 
    for(int i=1;i<=n;++i) 
    {
        for(int j=1;j<=m;++j) 
        {
            if(i>1 && mk[i][j] && mk[i-1][j]) 
            {
                up[i][j]=up[i-1][j]+1; 
                l[i][j]=max(l[i][j],l[i-1][j]); 
                r[i][j]=min(r[i][j],r[i-1][j]); 
            }
            ans=max(ans, (r[i][j]-l[i][j]+1)*up[i][j]); 
        }
    } 
    printf("%d
",ans*3); 
    return 0; 
}