USACO 1997 FALL Big Barn 方形牛棚

#include<cstdio>int n,m,x,y,f[1001][1001];bool a[1001][1001];int check(int x,int y,int k){if(x+k>n||y+k>n)return k-1;for(int i=x;i<=x+k;i++){if(a[i][y+k])return k-1;}for(int i=y;i<=y+k;i++){if(a[x+k][i])return k-1;}check(x,y,k+1);}int main(){freopen("bigbrn.in","r",stdin);freopen("bigbrn.out","w",stdout);scanf("%d%d",&n,&m);for(int i=1;i<=m;i++){scanf("%d%d",&x,&y);a[x][y]=true;}for(int i=1;i<=n;i++){for(int j=1;j<=n;j++){f[i][j]=check(i,j,1)+1;}}int max=0;for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)max=max>f[i][j]?max:f[i][j];printf("%d",max);fclose(stdin);fclose(stdout);return 0;}