luogu P1162 填涂颜色

https://www.luogu.org/problem/show?pid=1162

//其实很简单的吧
//就是最外圈加一圈0 ，然后把外圈里面的0都遍历了
//剩下的0 就变成2 就行了
#include<bits/stdc++.h>
using namespace std;
typedef pair <int,int> pii;
int n ,s[][];
bool vis[][];
int fx[]={-,,,};
int fy[]={,-,,};

bool check(int x,int y)
{
    if(!vis[x][y] && s[x][y] ==  && x>= && x<=n+ && y>= && y<=n+)
        return ;
    return ;
}

void bfs(int x,int y)
{
    queue<pii > que;
    que.push({x,y});
    //cout<<"yes1"<<endl;
    while (que.size() )
    {
        pii now = que.front(); que.pop();
        if( vis[now.first][now.second] )
            continue;
        vis[now.first][now.second] = ;//注意该点已经访问过   这里很容易忘记的吧
        //cout<<"yes2"<<endl;
        for(int i=;i<;i++)
        {
            //cout<<"yes3"<<endl;
            int dx= now.first+fx[i];
            int dy= now.second+fy[i];

            if(check(dx,dy))
            {
                //cout<<"yes3"<<endl;
                que.push({dx,dy});
            }
        }
    }
}

int main ()
{
    scanf("%d",&n);
    for(int i=;i<=n;i++)
        for(int j=;j<=n;j++)
            scanf("%d",&s[i][j]);
    //cout<<endl;
    //因为外圈已经本身就是0了
    //从第0行到第n+1行
    bfs(,);

    for(int i=;i<=n;i++)
    {
        for(int j=;j<=n;j++)
        {
            if( vis[i][j] )
                cout<<<<" ";
            else if(s[i][j] == )
                cout<<<<" ";
            else
                cout<<<<" ";
        }
        cout<<endl;
    }
}