Codeforces Round #536 (Div. 2) D. Lunar New Year and a Wander(bfs)

#include <bits/stdc++.h>
#define ll long long
using namespace std;
vector<int> v[100005];
bool vis[100005];
int n,m;

void bfs(){
  priority_queue<int,vector<int>,greater<int> > q;
  q.push(1);
  vis[1] = true;
  while(!q.empty()){
    int u = q.top();
    q.pop();
    printf("%d ", u);
    for(int i=0;i<v[u].size();i++){
      int x = v[u][i];
      if(vis[x] == false) q.push(x);
      vis[x] = true;
    }
  }
}

int main()
{
  memset(vis,false,sizeof(vis));
  scanf("%d%d",&n,&m);
  for(int i=0;i<m;i++){
    int x,y;
    scanf("%d%d",&x, &y);
    v[x].push_back(y);
    v[y].push_back(x);
  }
  bfs();
  return 0;
}