坑，说好的1e5，但其实会炸空间，1e3就够了

#include<bits/stdc++.h>
#define N 1100
using namespace std;
bool b[N][N], vis[N][N];
int p[5][3] = {{-1, 0}, {1, 0}, {0, 1}, {0, -1}}, n;
struct node{
    int x, y;
}q[N];
void bfs(int x, int y){
    int head = 1, tail = 1;
    q[tail].x = x; q[tail].y = y;
    tail++;
    while(head < tail){
        vis[q[head].x][q[head].y] = 1;
        for(int i = 0; i < 4; i++){
            int nx = q[head].x + p[i][0], ny = q[head].y + p[i][1];
            if(nx >= 1 && nx <= n  &&  ny >= 1 && ny <= n  &&  b[nx][ny]  &&  !vis[nx][ny]){
                q[tail].x = nx; q[tail].y = ny;  //入队
                tail++;
                vis[nx][ny] = 1;
            }
        }
        head++;  //队头出队 
    }
}
int main(){
    ios::sync_with_stdio(false);
    int cnt = 0;
    cin >> n;
    memset(vis, 0, sizeof(vis));
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= n; j++)cin >> b[i][j];
    }
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= n; j++){
            if(b[i][j] && !vis[i][j]){
                cnt++;
                bfs(i, j);
            }
        }
    }
    cout << cnt;
    return 0;
}

//这题目太坑爹了，说好的1*10^5，结果10^4就够了，1*10^5会爆空间
#include<bits/stdc++.h>
using namespace std;
int n,a[1005][1005],ans;
int dir[4][2]={{1,0},{0,1},{-1,0},{0,-1}};
bool vis[1005][1005];
void dfs(int x,int y)
{
    vis[x][y]=true;
    for(int i=0;i<4;i++)
    {
        int nx=x+dir[i][0];
        int ny=y+dir[i][1];
        if(a[nx][ny]==1&&!vis[nx][ny])
        {
            vis[nx][ny]=true;
            dfs(nx,ny);
        }
    }
}
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            cin>>a[i][j];
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
        {
            if(!vis[i][j]&&a[i][j]==1)
            {
                ans++;
                dfs(i,j);
            }
        }
    cout<<ans<<endl;
    return 0;
}