洛谷P1162 填涂颜色

蒟蒻第一次写bfs
别问我为啥第一次写
（以前发现dfs貌似是万能的
一道签到题

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<string>
#include<ctime>
#include<queue>
#include<set>
#include<stack>
#include<map>
#include<algorithm>
#define maxn 100001
#define INF 0x3f3f3f3f
#define inf 0x3f
#define maxm 1001
using namespace std;
int n,dx[]={-1,1,0,0},bx,by,dy[]={0,0,-1,1},vis[31][31],a[31][31];
queue<int>     q;
void bfs(int x,int y){
    vis[x][y]=1;
    q.push(x);
    q.push(y);
    while(!q.empty()){
        int u=q.front();
        q.pop();
        int v=q.front();
        q.pop();
        for(int i=0;i<4;i++){
                int xx=u+dx[i];
                int yy=v+dy[i];
                if(a[xx][yy]==0&&xx>0&&yy>0&&xx<=n&&yy<=n&&vis[xx]

[yy]==0){
                    vis[xx][yy]=1;
                    q.push(xx);
                   // q.pop();
                    q.push(yy);
                   // q.pop();
                }    
        }
    }
}
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            cin>>a[i][j];
            if(a[i][j]==1) vis[i][j]=1;
        }
    }
    for(int i=1;i<=n;i=i+n-1){
        for(int j=1;j<=n;j++){
            if(vis[i][j]) continue;
            bfs(i,j);
        }
    }
    for(int i=1;i<=n;i=i+n-1){
        for(int j=1;j<=n;j++){
            if(vis[j][i]) continue;
            bfs(j,i);
        }
    }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            if(vis[i][j]==0) cout<<"2"<<" ";
            else cout<<a[i][j]<<" ";
        }
        cout<<endl;
    }
    return 0;
}