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<iostream>
#include<vector>
#include<stack>
using namespace std;
static const int MAX = 100000;
static const int NIL = -1;

int n;
vector<int> G[MAX];
int color[MAX];

void dfs(int r, int c)
{
	stack<int> S;
	S.push(r);
	color[r] = c;
	while(!S.empty())
	{
		int u = S.top();
		S.pop();
		for(int i = 0; i < G[u].size(); i++)
		{
			int v = G[u][i];
			if(color[v] == NIL)
			{
				color[v] = c;
				S.push(v);
			}
		}
	}
}

void assignColor()
{
	int id = 1;
	for(int i = 0; i < n; i++)
		color[i] = NIL;
	for(int u = 0; u < n; u++)
	{
		if(color[u] == NIL)
			dfs(u, id++);
	}
}


int main()
{
	int s, t, m, q;
	cin >> n >> m;
	
	for(int i = 0; i < m; i++)
	{
		cin >> s >> t;
		G[s].push_back(t);
		G[t].push_back(s);
	}
	
	assignColor();
	
	cin >> q;
	for(int i = 0; i < q; i++)
	{
		cin >> s >> t;
		if(color[s] == color[t])
		{
			cout << "yes" << endl;
			
		}
		else
		 cout << "no" << endl;
	}
}

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

int main(){
  int n,m,q,a,b,s,t,k,h;
  vector<int> g[100001];
  queue<int> qu;
  set<int> ch;
  cin>>n>>m;
  for(int i=0;i<m;i++){
    cin>>a>>b;
    g[a].push_back(b);
    g[b].push_back(a);
  }
  cin>>q;
  for(int i=0;i<q;i++){
    cin>>s>>t;
    
    k=0; 
    ch.clear();
    while(qu.size()){
      qu.pop();
    }
    qu.push(s);
    
    while(qu.size()){//?????????
      n=qu.front();qu.pop();
      if(n==t){//???????????????
	cout<<"yes"<<endl;
	k++;
	break;
      }
      for(int j=0;j<g[n].size();j++){//????????????????????´????????????
	if(ch.count(g[n][j])==0 ){
	  qu.push(g[n][j]);
	  ch.insert(g[n][j]);
	}
      }
    }
    
    if(k==0)cout<<"no"<<endl;
  }
  return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
using namespace std;
static const int MAX = 100000;
int n;
int color[MAX];
vector<int> v[MAX];
void b(int s, int t){
	stack<int> S;
	S.push(s);
	int tp;
	color[s] = t;
	while (!S.empty()){
		int tp = S.top(); S.pop();
		for (int i = 0; i < v[tp].size(); i++){
			if (color[v[tp][i]] == MAX){
				color[v[tp][i]] = t;
				S.push(v[tp][i]);
			}
		}
	}
}
void a(){
	for (int i = 0; i < n; i++){
		color[i] = MAX;
	}
	int id = 0;
	for (int i = 0; i < n; i++){
		id++;
		if(color[i] == MAX)b(i,id);
	}
}
int main(){
	int m, s, t;
	int q;
	cin >> n >> m;
	for (int i = 0; i < m; i++){
		cin >> s >> t;
		v[s].push_back(t);
		v[t].push_back(s);
	}
	a();
	cin >> q;
	for (int i = 0; i < q; i++){
		cin >> s >> t;
		if (color[s] == color[t]) cout << "yes" << endl;
		else cout << "no" << endl;
 	}
	return 0;
}

C++: #include<stdio.h>
#include<queue>

#define MAX 10000

int G[MAX+1][MAX+1];
int n, m;

bool bfs(int src, int dest) {
    bool C[MAX];
    for (int i = 0; i < n; ++i) C[i] = false;

    std::queue<int> Q;
    Q.push(src);
    while(!Q.empty()) {
        int cur = Q.front();Q.pop();
        for (int i = 0; i < n; ++i) {
            if (G[cur][i] == 0) continue;
            if (C[i]) continue;
            if (i == dest) return true;
            Q.push(i);
            C[i] = true;
            //printf("s:%d, cur:%d, i:%d\n", src, cur, i);
        }
    }

    return false;
}

int main() {
    scanf("%d %d", &n, &m);
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            G[i][j] = 0;
        }
    }
    for (int i = 0; i < m; ++i) {
        int u,k;
        scanf("%d %d", &u, &k);
        G[u][k] = 1;
        G[k][u] = 1;
    }

    int q;
    scanf("%d", &q);
    for (int i = 1; i <= q; ++i) {
        int s,d;
        scanf("%d %d", &s, &d);
        bfs(s, d) ? printf("yes\n") : printf("no\n");
    }

    return 0;
}

C++: #include <bits/stdc++.h>
#define REP(i,n) for(int i=0;i<n;++i)
using namespace std;
const int MAX = 1e5;

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

void dfs(int r, int c) {
  color[r] = c;
  REP(i, G[r].size()) {
    int v = G[r][i];
    if (color[v] == -1) {
      color[v] = r;
      dfs(v, c);
    }
  }
}

int main() {
  int s, t, m, q, id = 0;
  cin >> n >> m;
  REP(i, m) {
    cin >> s >> t;
    G[s].push_back(t);
    G[t].push_back(s);
  }
  REP(i, n) color[i] = -1;
  REP(i, n) { if (color[i] == -1) dfs(i, id++); }
  cin >> q;
  REP(i, q) {
    cin >> s >> t;
    if (color[s] == color[t]) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }
  return 0;
}

C++: #import <iostream>
#import <vector>
#import <cassert>
#import <queue>

const int M = 10000000;

void connected_components(
  std::vector<std::vector<int> >& adj_list,
  std::vector<int>& component_numbers,
  int root, int current_component){
  assert(component_numbers[root] == M);

  std::queue<int> target_q;
  target_q.push(root);
  component_numbers[root] = current_component;
  // dist_q.push(0;)
  while(!target_q.empty()){
    int vtx = target_q.front(); target_q.pop();
    for(int const&  u : adj_list[vtx]){
      if(component_numbers[u] == M){
        target_q.push(u);
        component_numbers[u] = current_component;
      }
    }
  }
}

int main(int argc, char const *argv[]) {
  int n, m, q;
  std::cin >> n;
  std::cin >> m;

  std::vector<std::vector<int> > adj_list(n);

  for (size_t i = 0; i < m; i++) {
    int a, b;
    std::cin >> a;
    std::cin >> b;
    adj_list[a].push_back(b);
  }

  std::vector<int> component(n, M);

  for (size_t i = 0; i < n; i++) {
    if(component[i] == M){
      connected_components(adj_list, component, i, i);
    }
  }

  std::cin >> q;
  for(size_t i =0; i < q; i++){
    int a, b;
    std::cin >> a;
    std::cin >> b;
    bool in_same_component = (component[a] == component[b]);
    std::cout << (in_same_component ? "yes" : "no") << std::endl;
  }


  return 0;
}