BZOJ1057: [ZJOI2007]棋盘制作（洛谷P1169）

DP

#include<cctype>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define N 2005
#define F inline
using namespace std;
int n,m,ans1,ans2,h[N][N],l[N][N],r[N][N],L[N][N],R[N][N],s[N][N];
bool f[N][N];
F char readc(){
static char buf[100000],*l=buf,*r=buf;
if (l==r) r=(l=buf)+fread(buf,1,100000,stdin);
if (l==r) return EOF; return *l++;
}
F int _read(){
int x=0; char ch=readc();
while (!isdigit(ch)) ch=readc();
while (isdigit(ch)) x=(x<<3)+(x<<1)+(ch^48),ch=readc();
return x;
}
F void doit(){
memset(h,0,sizeof(h)),memset(s,0,sizeof(s));
memset(L,0,sizeof(L)),memset(R,0,sizeof(R));
memset(l,0,sizeof(l)),memset(r,0,sizeof(r));
for (int i=1;i<=n;i++){
for (int j=1,tem=0;j<=m;j++)
if (f[i][j]) L[i][j]=tem;
else tem=j,l[i][j]=0;
for (int j=m,tem=m;j;j--)
if (f[i][j]) R[i][j]=tem;
else tem=j,r[i][j]=m;
for (int j=1;j<=m;j++) r[0][j]=m;
for (int j=1;j<=m;j++)
if (f[i][j]){
h[i][j]=h[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]);
s[i][j]=min(s[i-1][j-1],min(s[i-1][j],s[i][j-1]))+1;
ans1=max(ans1,s[i][j]*s[i][j]);
ans2=max(ans2,(r[i][j]-l[i][j]-1)*h[i][j]);
}
}
}
int main(){
n=_read(),m=_read();
for (int i=1;i<=n;i++)
for (int j=1;j<=m;j++){
f[i][j]=_read();
if ((i+j)%2==0) f[i][j]^=1;
}
doit();
for (int i=1;i<=n;i++)
for (int j=1;j<=m;j++)
f[i][j]^=1;
doit();
return printf("%d\n%d\n",ans1,ans2),0;
}