Go: package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
)

// Node 頂点
type Node struct {
	gid  int   // グループID
	edge []int // 隣接辺
}

// NoID グループIDなし
const NoID = -1

// NewNode 頂点の生成
func NewNode() *Node {
	return &Node{gid: NoID, edge: []int{}}
}

func parseNode(nodes []*Node, gid int, queue []int) {
	if len(queue) == 0 {
		return
	}
	var nextQ []int
	for _, id := range queue {
		node := nodes[id]
		if node.gid == NoID {
			node.gid = gid
			for _, edge := range node.edge {
				nextQ = append(nextQ, edge)
			}
		}
	}
	parseNode(nodes, gid, nextQ)
	return
}
func digNode(nodes []*Node, id, gid int) {
	node := nodes[id]
	if node.gid != NoID {
		// 探索済み
		return
	}
	node.gid = gid
	for _, edge := range node.edge {
		digNode(nodes, edge, gid)
	}
	return
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	n, m := eGetInt2(scanner)

	nodes := make([]*Node, n)
	for i := 0; i < n; i++ {
		nodes[i] = NewNode()
	}

	for i := 0; i < m; i++ {
		a, b := eGetInt2(scanner)
		nodes[a].edge = append(nodes[a].edge, b)
		nodes[b].edge = append(nodes[b].edge, a)
	}

	for i := 0; i < n; i++ {
		// 幅優先探索
		// gid := i
		// queue := []int{i}
		// parseNode(nodes, gid, queue)

		// 深さ優先探索
		digNode(nodes, i, i)
	}

	q := eGetInt(scanner)
	for i := 0; i < q; i++ {
		a, b := eGetInt2(scanner)
		if nodes[a].gid == nodes[b].gid {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func eGetInt(scanner *bufio.Scanner) int {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0]
}
func eGetInt2(scanner *bufio.Scanner) (int, int) {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0], t[1]
}

func eGetline(p *bufio.Scanner) string {
	if !p.Scan() {
		if err := p.Err(); err != nil {
			log.Fatal(err.Error())
		}
		return ""
	}
	return p.Text()
}

func eAtoi(s []string) []int {
	ints := make([]int, len(s))
	var err error
	for i, e := range s {
		ints[i], err = strconv.Atoi(e)
		if err != nil {
			log.Fatal(err.Error())
		}
	}
	return ints
}

C++: #include <bits/stdc++.h>

using namespace std;

#define nil -1
vector<vector<int>> makelist(int n, int m) {
	vector<vector<int>> Adjlist(n);
	int a, b;

	for(int i = 0; i < m; i++) {
		cin >> a >> b;
		Adjlist[a].push_back(b);
		Adjlist[b].push_back(a);
	}

	return Adjlist;
}

void dfs_run(int start, int id, vector<vector<int>>& adj, vector<int>& color) {
	//cout << start << endl;
	while(!adj[start].empty()) {
		int tmp;
		tmp = adj[start].back();
		adj[start].pop_back();	
		if(color[tmp] != nil) {
			continue;
		}
		color[tmp] = id;
		dfs_run(tmp, id, adj, color);
	}
}

void dfs(int n, vector<vector<int>>& adj, vector<int>& color) {
	int id = 0;
	for(int i = 0; i < n; i++) {
		if(color[i] == nil) {
			color[i] = i;
			dfs_run(i, id, adj, color);
		}
		id++;
	}
	/*for(int i = 0; i < n; i++) {
		cout << color[i] << endl;
	}*/
	
}

int main(void)
{
	int n, m, q;

	cin >> n >> m;
	vector<vector<int>> Adjlist = makelist(n, m);
	vector<int> color(n, nil);

	dfs(n, Adjlist, color);
	cin >> q;
	for(int i = 0; i < q; i++) {
		int a, b;
		cin >> a >> b;

		if(color[a] == color[b]) {
			cout << "yes" << endl;
		}else{
			cout << "no" << endl;
		}
	}

	return 0;
}

C++: #include <iostream>
#include <vector>
using namespace std;

bool search(vector<int> member,int x){
  for(int i=0; i<member.size(); i++){
    if(member[i] == x)
      return true;
  }
    return false;
}
vector<int> update(vector<int> mother,vector<int> children,int join[],int a,int b){
  mother.push_back(b);
  join[b] = join[a];
  for(int i=0; i<children.size(); i++){
    int num=children[i];
    mother.push_back(num);
    join[num] = join[a];
  }

  return mother;
}
int main(){
  int n,m,join[10000],s,t;
  vector<int> group[10000];
  cin >> n >> m;

  for(int i=0; i<n; i++)
    join[i] = i;
    
  for(int i=0; i<m; i++){
    cin >> s >> t;
    bool flag = search(group[join[t]],s);

    if(!flag){
      int x = join[t];
      int y = join[s];

      if(x!=t || !group[x].empty())
	group[x] = update(group[x],group[y],join,x,y);


      else{
	group[y].push_back(t);
	join[x] = y;
      }
    }

  }
 
  int q;
  cin >> q;
  
  bool answer[10000];
  for(int i=0; i<q; i++){
    cin >> s >> t;
    
    if(join[s] == join[t])
      answer[i]=true;
    else
      answer[i]=false;
  }

  for(int i=0; i<q; i++){
    if(answer[i])
      cout << "yes\n";
    else
      cout << "no\n";
  }
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
#define N 100000

using namespace std;
vector<int> v[N];
int group[N]={};
int g=0;

bool search(int s,int t){
  if(group[s]==group[t]&&group[s]>0) return true;
  group[s]=++g;
  queue<int> q;
  q.push(s);
  while(!q.empty()){
    int a=q.front();
    for(auto i=v[a].begin();i!=v[a].end();i++){
      if(group[*i]==0){
        group[*i]=g;
        q.push(*i);
      }
    }
    q.pop();
  }
  if(group[s]==group[t]&&group[s]>0){ 
    return true;
  }else{
    return false;
  }
}

int main(){
  int n,m; cin>>n>>m;
  int s,t;
  for(int i=0;i<m;i++){
    cin>>s>>t;
    v[s].push_back(t);
    v[t].push_back(s);
  }

  int q; cin>>q;
  for(int i=0;i<q;i++){
    cin>>s>>t;
    if(search(s,t)){
      cout<<"yes"<<endl;
    }else{
      cout<<"no"<<endl;
    }
  }

}

C++: #include <cassert>
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <algorithm>
#include <bitset>
#include <complex>

#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#define rep(i,n) for(int i=0;i<(n); i++)
#define rep2(i,n) for(int i=1;i<=(n);i++)
#define WHITE 0
#define GRAY 1
#define BLACK 2

using namespace std;
typedef long long ll;
const int NMAX = 100000;
const int k = 200000;
static const int INF = 1<<21;
static const int NIL = -1;

int dp[3001][3001];
ll gcd(ll a, ll b){
if(a<b) swap(a,b);
    if(b==0) return a;
    return gcd(b, a%b);
}

int n,color[NMAX];
vector<int> G[NMAX];

void dfs(int r,int c){
    stack<int> S;
    S.push(r);
    color[r] = c;
    while(!S.empty()){
        int u=S.top();
        S.pop();
        rep(i,G[u].size()){
            int v=G[u][i];
            if(color[v]==NIL){
                color[v]=c;
                S.push(v);
            }
        }
    }
}

void assignColor(){
    int id=1;
    rep(i,n) color[i]=NIL;
    rep(u,n){
        if(color[u]==NIL){
            dfs(u,id++);
        }
    }
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0); //この2行はより速度を向上させる
    // 追加２, 以降 cin の入力元が 'input.txt' になる


    int m,s,t,q;
    cin >> n >> m;
    rep(i,m){
        cin >> s >> t;
        G[s].push_back(t);
        G[t].push_back(s); //無向グラフなので双方に格納する
    }
    assignColor(); //色塗り

    cin >> q;

    rep(i,q){
        cin >> s >> t;
        if(color[s]==color[t]){
            cout << "yes" << endl;
        }else{
            cout << "no" << endl;
        }
    }
    return 0;
}