记录编号	556972	评测结果	AAWWWWAAWWA
题目名称	[USACO Oct09] 乳草的入侵	最终得分	45
用户昵称	数声风笛ovo	是否通过	未通过
代码语言	C++	运行时间	0.006 s
提交时间	2020-10-31 23:37:31	内存使用	3.78 MiB

#include<bits/stdc++.h>
#define ll long long
#define re register int
#define pp cout<<"qwq"
using namespace std;
const int maxn=1e2+9;
int m,n,x,y,ans=0; 
int a[maxn][maxn]={0};
bool b[maxn][maxn]={0};
void dfs(int nx,int ny){
	if(nx<=0||nx>n||ny<=0||ny>m) return ;
	if(a[nx][ny]||b[nx][ny]) return ;
	b[nx][ny]=1;
	dfs(nx+1,ny+1);
	dfs(nx+1,ny);
	dfs(nx+1,ny-1);
	dfs(nx-1,ny+1);
	dfs(nx-1,ny);
	dfs(nx-1,ny-1);
	dfs(nx,ny+1);
	dfs(nx,ny-1);
}
bool flood(){
	for(re i=1;i<=n;i++){
		for(re j=1;j<=m;j++){
			if(!a[i][j]) return true;
		}
	}
	return false;
}
void week(){
	a[x][y]=114514;
	while(flood()){
	ans++;
	for(re i=1;i<=n;i++){
		for(re j=1;j<=m;j++){
			b[i][j]=0;
		}
	}
	for(re i=1;i<=n;i++){
		for(re j=1;j<=m;j++){
			if(!a[i][j]){
				if(a[i-1][j]==114514||a[i+1][j]==114514||a[i][j-1]==114514||a[i][j+1]==114514||a[i-1][j-1]==114514||a[i-1][j+1]==114514||a[i+1][j-1]==114514||a[i+1][j+1]==114514||a[i+1][j+1]==114514) b[i][j]=1;
				}
			}
		}
		for(re i=1;i<=n;i++){
			for(re j=1;j<=m;j++){
				 if(b[i][j]){
				 	a[i][j]=114514;
				 }
			}
		}
	}
	return ;	    
}
int main(){
	freopen("milkweed.in","r",stdin);
	freopen("milkweed.out","w",stdout);
	scanf("%d%d%d%d",&m,&n,&x,&y);
	for(re i=n;i>=1;i--){
		string p;
		cin>>p;
		for(re j=0;j<m;j++){
			if(p[j]=='*') a[i][j+1]=1;
			else a[i][j+1]=0;
		}
	}
	dfs(x,y);
	for(re i=1;i<=n;i++){
		for(re j=1;j<=m;j++){
			//cout<<a[i][j];
			if(!a[i][j]&&!b[i][j]){
				printf("-1\n");
				return 0;
			}
		}
		//cout<<"\n";
	}
	week();
	printf("%d\n",ans);
	return 0;
}