POJ 3494 Largest Submatrix of All 1’s（最大子图形）

#include <cstdio>
#include <cstring>
using namespace std;
const int N=2010;
int i,j,n,m,ans,l
,r
,h
,lmax,rmax,a

;
int main(){
while(~scanf("%d%d",&n,&m)){
ans=0;
memset(h,0,sizeof(h));
for(int i=1;i<=n;i++)for(int j=1;j<=m;j++)scanf("%d",&a[i][j]);
for(int i=1;i<=m;i++)l[i]=1,r[i]=m;
for(int i=1;i<=n;i++){
for(lmax=j=1;j<=m;j++)if(a[i][j]){
h[j]++;
if(lmax>l[j])l[j]=lmax;
}else h[j]=0,l[j]=1,r[j]=m,lmax=j+1;
for(rmax=j=m;j;j--)if(a[i][j]){
if(rmax<r[j])r[j]=rmax;
if((r[j]-l[j]+1)*h[j]>ans)ans=(r[j]-l[j]+1)*h[j];
}else rmax=j-1;
}printf("%d\n",ans);
}return 0;
}