Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N, M := sc.nextInt(), sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < M; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	group := make([]int, N)
	for i := 0; i < N; i++ {
		group[i] = -1
	}
	var dfs func(cur int)
	dfs = func(cur int) {
		for i := 0; i < len(G[cur]); i++ {
			next := G[cur][i]
			if group[next] == -1 {
				group[next] = group[cur]
				dfs(next)
			}
		}
	}
	num := 0
	for i := 0; i < N; i++ {
		if group[i] == -1 {
			group[i] = num
			dfs(i)
			num++
		}
	}

	Q := sc.nextInt()
	for i := 0; i < Q; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		if group[s] == group[t] {
			fmt.Fprintln(wtr, "yes")
		} else {
			fmt.Fprintln(wtr, "no")
		}
	}
	wtr.Flush()
}

C++: #include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<queue>
#include<vector>
using namespace std;
#define MAX 100000

int d[MAX];
vector<int> V[MAX];
int tt=0,n,m;
queue<int> Q;

void gogo(int x){
  Q.push(x);
  d[x]=tt;
  int v;

  while(!Q.empty()){
    v=Q.front(); Q.pop();
    for(int i=0;i<V[v].size();i++){
      if(d[V[v][i]]==-1) {
        Q.push(V[v][i]);
        d[V[v][i]]=d[v];

      }
    }
  }

}

void gostart(){
  for(int i=0;i<n;i++){
    if(d[i]==-1) {
      gogo(i);
      tt++;
    }
  }
}

int main()  {
  cin>>n>>m;
  for(int i=0;i<n;i++){
    d[i]=-1;
  }

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

  gostart();

  int q;
  cin>>q;
  int k,l;
  for(int i=0;i<q;i++){
    cin>>k>>l;
    if(d[k]==d[l]) cout<<"yes"<<endl;
    else cout<<"no"<<endl;
  }
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <list>

class Graph{
public:
	std::vector< std::vector<int> > A;
	std::vector<int> Cluster;
	int n;

	Graph(int n);

	bool isConnected(int s, int t);

	void MakeCluster();

	void Link(int s, int t);

};

Graph::Graph(int n){
	A.resize(n);
	Cluster.resize(n);
	for (int i = 0; i < n; i++) Cluster[i] = 0;
	this->n = n;
}

void Graph::Link(int s, int t){
	A[s].push_back(t);
	A[t].push_back(s);
	return;
}

void Graph::MakeCluster(){
	int clusternum = 0;
	std::list<int> Q;
	for (int i = 0; i < n; i++){
		if (Cluster[i] == 0){
			Q.clear();
			clusternum++;
			Cluster[i] = clusternum;
			Q.push_back(i);
			bool res = false;
			while (!Q.empty()){
				int f = Q.front();
				Q.pop_front();
				for (std::vector<int>::iterator itr = A[f].begin(); itr != A[f].end(); itr++){
					if (Cluster[*itr] == false){
						Cluster[*itr] = clusternum;
						Q.push_back(*itr);
					}
				}
			}
		}
	}
	return;
}

bool Graph::isConnected(int s, int t){
	return Cluster[s] == Cluster[t];
}

int main(){
	int n, m, s, t, q;
	scanf("%d%d", &n, &m);
	Graph G(n);
	for (int i = 0; i < m; i++){
		scanf("%d%d", &s, &t);
		G.Link(s, t);
	}
	scanf("%d", &q);
	G.MakeCluster();
	for (int i = 0; i < q; i++){
		scanf("%d%d", &s, &t);
		if (G.isConnected(s, t)) printf("yes\n"); else printf("no\n");
	}
	
	return 0;
}

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

int a[100000];
int search(int k){
  if(a[k]==k){
      return k;
  }
  int p=search(a[k]);
  a[k]=p;
  return p;
}

int main(){
  for(int i=0;i<100000;i++){
    a[i]=i;
  }
  int n,m,p,q,r,s,t;
  cin>>n>>m;
  for(int i=0;i<m;i++){
    cin>>p>>q;
    a[search(p)]=search(q);
  }
  cin>>r;
  for(int i=0;i<r;i++){
    cin>>s>>t;
    if(search(s)==search(t)){
        cout<<"yes"<<endl;
    }
    else{
        cout<<"no"<<endl;
    }
  }
  return 0;
}

C++: #include <iostream>
#include <queue>
using namespace std;
struct Node{
    vector<int> fri;
    bool flag;
};
queue<Node> refresh(queue<Node> que,Node node[],int n){
    while(!que.empty()){
        que.pop();
    }
    for(int i=0; i<n; i++)
        node[i].flag=false;

    return que;
}

int main(){
    int n,m,s,t;
    Node node[100000];
    cin >> n >> m;

    for(int i=0; i<m; i++){
        cin >> s >> t;

        node[s].fri.push_back(t);
        node[t].fri.push_back(s);
    }

    queue<Node> que;
    refresh(que,node,n);

    int q;
    cin >> q;

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

        node[s].flag=true;
        que.push(node[s]);

        while(!que.empty() && !answer[i]){
         Node fro = que.front();

         for(int j=0; j<fro.fri.size(); j++){
            int x = fro.fri[j];
  
            if(x==t){
                answer[i]=true;
                break;
            }

            if(!node[x].flag){
                node[x].flag=true;
                que.push(node[x]);
            }
         }

          que.pop();
        }

        que=refresh(que,node,n);
    }

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

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

using namespace std;

#define REP(i, n) for(int i = 0; i < n; i++)

int n, m;
vector<int> G[100000];
int id[100001];
int visit[100001] = {0};
int s, t;

void check(int x, int u) {
    visit[x] = 1;
    id[x] = u;

    int v;
    REP(i, G[x].size()) {
        v = G[x][i];
        if (visit[v] == 0) check(v, u);
    }
}

int main() {
    cin >> n >> m;
    int a, b;
    REP(i, m) {
        cin >> a >> b;
        G[a].push_back(b);
        G[b].push_back(a);
    }

    REP(i, n) {
        if (visit[i] == 0) check(i, i);
    }

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