[ZJOI2007]棋盘制作

题面

dp悬线法

#include<bits/stdc++.h>
#define IL inline
#define RI register int
#define maxn 2001
using namespace std;
IL void read(int &x){
    int f=1;x=0;char s=getchar();
    while(s>'9'||s<'0'){if(s=='-')f=-1;s=getchar();}
    while(s<='9'&&s>='0'){x=x*10+s-'0';s=getchar();}
    x*=f;
}
int res[maxn][maxn],left[maxn][maxn],right[maxn][maxn],up[maxn][maxn];
int n,m,ans1,ans2;
int main()
{
    read(n),read(m);
    for(RI i=1;i<=n;i++)
        for(RI j=1;j<=m;j++)
            {
                read(res[i][j]);
                left[i][j]=right[i][j]=j;
                up[i][j]=1;
            }
    for(RI i=1;i<=n;i++)
        for(RI j=2;j<=m;j++)
            if(res[i][j]!=res[i][j-1])
                left[i][j]=left[i][j-1];
    for(RI i=1;i<=n;i++)
        for(RI j=m-1;j>0;j--)
            if(res[i][j]!=res[i][j+1])
                right[i][j]=right[i][j+1];
    for(RI i=1;i<=n;i++)
        for(RI j=1;j<=m;j++)
            {
                if(i>1&&res[i][j]!=res[i-1][j])
                {
                    left[i][j]=max(left[i][j],left[i-1][j]);
                    right[i][j]=min(right[i][j],right[i-1][j]);
                    up[i][j]=up[i-1][j]+1;
                }
                int a=right[i][j]-left[i][j]+1; 
                int b=min(a,up[i][j]);
                //printf("a:%d b:%d\n",a,b);
                ans1=max(ans1,b*b);
                ans2=max(ans2,a*up[i][j]);
            }
    printf("%d\n%d",ans1,ans2);
}