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 <queue>
#include <vector>

using namespace std;

int main() {
  vector<int> R[100000];
  queue<int> Q;
  int n,m,s,t,q;
  int visit[100000];

  cin >> n >> m;
  for(int i=0;i<m;i++){
    cin >> s >> t;
    R[s].push_back(t);
    R[t].push_back(s);
  }
  cin >> q;
  for(int i=0;i<q;i++){
    cin >> s >> t;
    for(int j=0;j<n;j++) visit[j] = 0;
    Q.push(s);
    int f=0;
    while(Q.empty() == false){
      int u = Q.front();
      Q.pop();
      visit[u] = 1;
      if(u==t){
	f = 1;
      }
      for(int j=0;j<R[u].size();j++){
	int v = R[u][j];
	if(visit[v]==0) Q.push(v);
      }
    }
    if(f==1) cout << "yes" << endl;
    else cout << "no" << endl;
  }

  return 0;
}

C++: #include<stdio.h>
#include<stdlib.h>
#define MAX 100000000
#define NIL -1

int G[MAX][MAX];
int n, color[MAX], N[MAX], top=0;


void push(int x) {
  N[++top]=x;
}

int pop() {
  top--;
  return N[top+1];
}

int isEmpty() {
  return top==0;
}

void dfs(int r, int c) {
  int i, v, u;
  push(r);
  color[r]=c;
  while (! isEmpty()) {
    u=N[top];
    pop();
    for (i=0; i<n; i++) {
      if (G[u][i]==0) continue;
        v=i;
      if (color[v]==NIL) {
        color[v]=c;
        push(v);
      }
    }
  }
}



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

int main() {

  int  m, i, j, v, s, t, q;

  scanf("%d %d", &n, &m);

  for (i=0; i<n; i++)
    for (j=0; j<n; j++)
      G[i][j]=0;

  for (i=0; i<m; i++) {
    scanf("%d %d", &s, &t);
    G[s][t]=1;
    G[t][s]=1;
  }
  assignColor();

  scanf("%d", &q);

  for (i=0; i<q; i++) {
    scanf("%d %d", &s, &t);
    if (color[s]== color[t]) {
      printf("yes\n");
    } else {
      printf("no\n");
    }
  }

  return 0;

}

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

#define REP(i, n) for(int i=0;i<(int)(n);i++)
#define ALL(x) (x).begin(),(x).end()
const int INF = 1e9;

using namespace std;
int n, m;
struct node {
    int parent;
    vector<int> child;
};

int main() {
    cin >> n >> m;
    node person[n];
    REP(i, n)
        person[i].parent = -1;
    REP(i, m){
        int s, t;
        cin >> s >> t;
        if(person[s].parent == -1 && person[t].parent == -1){
            person[s].parent = s;
            person[t].parent = s;
            person[s].child.push_back(t);
        } else if(person[s].parent == -1){
            person[s].parent = person[t].parent;
            person[t].child.push_back(s);
        } else if(person[t].parent == -1){
            person[t].parent = person[s].parent;
            person[s].child.push_back(t);
        } else {
            person[t].parent = person[s].parent;
            REP(j, person[t].child.size()){
                person[person[t].child[j]].parent = person[s].parent;
                person[person[s].parent].child.push_back(person[t].child[j]);
            }
        }
    }
    int q;
    cin >> q;
    REP(i, q){
        int s, t;
        cin >> s >> t;
        if(person[s].parent != -1 && person[t].parent != -1  && person[s].parent == person[t].parent)
            cout << "yes" << endl;
        else
            cout << "no" << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <queue>
#include <vector>

using namespace std;

const int N = 100000;
int n;
// int color[N];
int group[N];
vector<int> v[N];

void setColor(int r, int c){
  queue<int> q;
  q.push(r);
  group[r] = c;

  while(!q.empty()){
    int x = q.front(); q.pop();
    for(int i=0;i<v[x].size();i++){
      int y = v[x][i];
      if(group[y] == -1){
        q.push(y);
        group[y] = c;
      }
    }
  }
}

void assignColor(){
  int id = 1;
  for(int i=0;i<n;i++) group[i] = -1;
  for(int u=0;u<n;u++){
    if(group[u] == -1) setColor(u, id++);
  }
}

int main(){
  int 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);
  }
  assignColor();

  int qn; cin >> qn;
  for(int i=0;i<qn;i++){
    cin >> s >> t;
    if(group[s] == group[t]) cout << "yes" << endl;
    else cout << "no" << endl;
  }
  return 0;
}