bzoj1057: [ZJOI2007]棋盘制作

#include<cstdio>
#include<cstring>
#include<cctype>
#include<algorithm>
using namespace std;
#define rep(i,s,t) for(int i=s;i<=t;i++) 
#define dwn(i,s,t) for(int i=s;i>=t;i--)
#define clr(x,c) memset(x,c,sizeof(x))
int read(){
    int x=0;char c=getchar();
    while(!isdigit(c)) c=getchar();
    while(isdigit(c)) x=x*10+c-‘0‘,c=getchar();
    return x;
}
const int nmax=2005;
int a[nmax][nmax],b[nmax][nmax],n,m;
struct node{
    int x,h;
    node(){}
    node(int x,int h):x(x),h(h){};
};
node s[nmax];
void print(){
    rep(i,1,n){
        rep(j,1,m) printf("%d ",a[i][j]);printf("\n");
    }
    rep(i,1,n) {
        rep(j,1,m) printf("%d ",b[i][j]);printf("\n");
    }
}
void maxs(int &a,int b){
    if(a<b) a=b;
}
int main(){
    n=read(),m=read();
    rep(i,1,n) rep(j,1,m){
        a[i][j]=read();
        if((i+j)%2) a[i][j]^=1;
    }
    rep(i,1,n) rep(j,1,m) b[i][j]=a[i][j]==0?b[i][j-1]+1:0;
    //print();
    int ans=0,res=0,top,tmp;
    rep(j,1,m){
        top=0;
        rep(i,1,n+1){
            tmp=i;
            while(top&&s[top].h>b[i][j]){
                maxs(ans,min(i-s[top].x,s[top].h)*min(i-s[top].x,s[top].h));
                maxs(res,s[top].h*(i-s[top].x));
                tmp=s[top--].x;
            }
            s[++top]=node(tmp,b[i][j]);
        }
    }
     
    rep(i,1,n) rep(j,1,m) a[i][j]^=1;
    rep(i,1,n) rep(j,1,m) b[i][j]=a[i][j]==0?b[i][j-1]+1:0;
    //print();
    rep(j,1,m){
        top=0;
        rep(i,1,n+1){
            tmp=i;
            while(top&&s[top].h>b[i][j]){
                maxs(ans,min(i-s[top].x,s[top].h)*min(i-s[top].x,s[top].h));
                maxs(res,s[top].h*(i-s[top].x));
                tmp=s[top--].x;
            }
            s[++top]=node(tmp,b[i][j]);
        }
    }
    printf("%d\n%d\n",ans,res);
    return 0;
}