其余 WA。

#include<bits/stdc++.h>
using namespace std;
const int N=5e4+1;
vector<int>vec[N];
int n,m;
queue<int>q;
map<pair<int,int> , bool>jl,vis;
void dfs(int u){
	for(auto v:vec[u]){
		if(!vis[{u,v}]){
			vis[{u,v}]=1;
			dfs(v);
		}
	}
	q.push(u);
}
signed main(){
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		int u,v;
		cin>>u>>v;
		if(jl[{u,v}] || jl[{v,u}])continue;
		vec[u].push_back(v);
		vec[v].push_back(u);
		jl[{u,v}]=1;
		jl[{v,u}]=1;
	}
	dfs(1);
	while(!q.empty()){
		cout<<q.front()<<'\n';
		q.pop();
	} 
	return 0;
}