https://codeforces.com/contest/1176/problem/E
C++版本一
题解:二分图01染色
C++版本二
题解:贪心
/*
*@Author: STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=200000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
int ans,cnt,flag,temp,sum;
int vis[N],c[N];
char str;
struct node{};
vector<int>G[N];
int main()
{
#ifdef DEBUG
freopen("input.in", "r", stdin);
//freopen("output.out", "w", stdout);
#endif
//ios::sync_with_stdio(false);
//cin.tie(0);
//cout.tie(0);
scanf("%d",&t);
while(t--){
scanf("%d%d",&n,&m);
for(int i=1;i<=n;i++)G[i].clear(),vis[i]=0,c[i]=0;
for(int i=1;i<=m;i++){
scanf("%d%d",&u,&v);
G[u].push_back(v);
G[v].push_back(u);
}
sum=0;
for(int i=1;i<=n;i++){
if(!vis[i]){
c[i]=1;++sum;
vis[i]=1;
for(int j=0,k=G[i].size();j<k;j++){
vis[G[i][j]]=1;
}
}
}
ans=sum<=n/2;
cout<<(ans?sum:n-sum)<<endl;
for(int i=1;i<=n;i++){
if(ans==c[i])printf("%d ",i);
}
cout<<endl;
}
#ifdef DEBUG
printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
//cout << "Hello world!" << endl;
return 0;
}