pay attention to the cout
#include <iostream>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;
const int maxn = 1010;
int nV,nE;
int vis[maxn];
int map[maxn][maxn];
int main() {
int st;
cin>>nV>>st;
for (int i=1;i<=nV;i++)
for (int j=1;j<=nV;j++) {
cin>>map[i][j];
}
queue<int >Q;
Q.push(st);
vis[st] = 1;
while(!Q.empty()) {
int tmp = Q.front();Q.pop();
for (int i=1;i<=nV;i++) {
if(map[tmp][i]&&!vis[i]) {
vis[i] = 1;
Q.push(i);
}
}
cout<<tmp;
if(!Q.empty()) cout<<" ";
}
}
“`