```c
#include<bits/stdc++.h>
using namespace std;
struct pos
{
int x;
int y;
};
bool mark[32][32];
int pic[32][32],dx[]= {0,0,1,-1},dy[]= {1,-1,0,0},n;
queue<pos>q;
void bfs(int x,int y)
{
int tx,ty;
q.push(pos{x,y});
mark[x][y]=true;
while(!q.empty())
{
tx=q.front().x;
ty=q.front().y;
q.pop();
for(int i=0; i<4; i++)
{
if(tx+dx[i]<0||ty+dy[i]<0||tx+dx[i]>n+1||ty+dy[i]>n+1||mark[tx+dx[i]][ty+dy[i]])continue;
q.push(pos{tx+dx[i],ty+dy[i]});
mark[tx+dx[i]][ty+dy[i]]=true;
}
}
}
int main()
{
memset(pic,0,sizeof(pic));
memset(mark,0,sizeof(mark));
cin>>n;
for(int i=1;i<=n;i++)
{
for(int j=1;j<=n;j++)
{
cin>>pic[i][j];
mark[i][j]=pic[i][j];
}
}
bfs(0,0);
for(int i=1;i<=n;i++)
{
for(int j=1;j<=n;j++)
{
if(mark[i][j])cout<<pic[i][j]<<" ";
else cout<<"2"<<" ";
}
cout<<endl;
}
}
```
by 123huchenghao @ 2024-06-28 18:30:38
*非常感谢！*
@[123huchenghao](/user/1380409)
by yanhaoming @ 2024-06-28 20:31:18