我是用广搜做的，测试点4WA了

#include<iostream>
#include<queue> 
using namespace std;
int map[31][31];
int vis[31][31];
int n;
int dx[4]={1,0,0,-1};
int dy[4]={0,1,-1,0};
struct point
{
	int x,y;
};
point now,en;
queue<point> q;
void bfs(int x,int y)
{
	now.x=x;now.y=y;
	vis[x][y]=1;
	if(map[x][y]==0) map[x][y]=3;
	q.push(now);
	while(!q.empty())
	{
		now=q.front();
		q.pop();
		for(int i=1;i<=n;++i)
		  {
		  	en.x=now.x+dx[i];
		  	en.y=now.y+dy[i];
		  	if(en.x>=1&&en.x<=n&&en.y>=1&&en.y<=n&&vis[en.x][en.y]==0&&map[en.x][en.y]==0)
		  	  {
		  	  	vis[en.x][en.y]=1;
		  	  	map[en.x][en.y]=3;
		  	  	q.push(en);
			  }
		  }
	}
}
int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;++i)
	  for(int j=1;j<=n;++j)
	    	scanf("%d",&map[i][j]);
	for(int i=1;i<=n;++i)
	  {
	  	if(map[1][i]==0) bfs(1,i);
	  	if(map[i][1]==0) bfs(i,1);
	  	if(map[n][i]==0) bfs(n,i);
	  	if(map[i][n]==0) bfs(i,n);
	  }
	for(int i=1;i<=n;++i)
	  {
	  	for(int j=1;j<=n;++j)
	  	  {
	  	  	if(map[i][j]==0) printf("2 ");
	  	  	if(map[i][j]==1) printf("1 ");
	  	  	if(map[i][j]==3) printf("0 ");
			}
	  	printf("\n");
	  }
	return 0;
}