[USACO5.3]巨大的牛棚Big Barn

明显DP，包括括号11行。
方程：

fi,j=⎧⎩⎨⎪⎪⎪⎪⎪⎪⎪⎪0min⎧⎩⎨⎪⎪fi−1,jfi−1,j−1fi,j−1mapi,j=0mapi,j≠0

#define N 1010int n,ans,ap[N][N],f[N][N];int main(){    n=read();    fr(i,1,read())        ap[read()][read()]=1;    fr(i,1,n)        fr(j,1,n)            if(!ap[i][j])                ans=max(ans,f[i][j]=min(min(f[i-1][j],f[i-1][j-1]),f[i][j-1])+1);    printf("%d\n",ans);    return 0;}