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<vector>
#include<iostream>
using namespace std;

#define MAX_N 100000
int par[MAX_N];//親の要素
int rank_[MAX_N];

//n要素で初期化
void init(int n)
{
	for (int i = 0; i < n; i++)
	{
		par[i] = i;
		rank_[i] = 0;
	}
}

//木の根を求める
int root(int x)
{
	if (par[x] == x)
	{
		return x;
	}
	else
	{
		return par[x] = root(par[x]);
	}
}

//xとyが同じ集合に属するか　否か
bool same(int x, int y)
{
	return root(x) == root(y);
}

//xとyの属する集合を併合
void unite(int x, int y)
{
	x = root(x);
	y = root(y);
	if (x == y)
	{
		return;
	}

	if (rank_[x] < rank_[y])
	{
		par[x] = y;
	}
	else
	{
		par[y] = x;
		if (rank_[x] == rank_[y])
		{
			rank_[x]++;
		}
	}


}

int main()
{
	int n;
	cin >> n;//頂点の数
	int m;
	cin >> m;//辺の数

	//初期化
	init(n);

	//木を作る
	for (int i = 0; i < m; i++)
	{
		int a, b;
		cin >> a >> b;
		if (same(a, b))
		{
			continue;
		}
		else
		{
			unite(a, b);
		}
	}

	int q;//クエリの数
	cin >> q;

	for (int i = 0; i < q; i++)
	{
		int a, b;
		cin >> a >> b;
		if (same(a, b))
		{
			cout << "yes" << endl;
		}
		else if(!same(a, b))
		{
			cout << "no" << endl;
		}
	}

	return 0;





}

C++: #include <iostream>
#include <stack>
#define N 100005


using namespace std;
int M[N][N];
int color[N];
int m, n;
int s, t, q;
int i, j;
int nt[N];
int next(int u){
	for(int v = nt[n]; v < n; v++){
		nt[u] = v + 1;
		if(M[u][v] && color[v] == 0) return v;
	}
	return -1;
}
int dfs(int s, int t){
	stack <int> S;
	S.push(s);
	color[s] = 1;
	while( !S.empty() ){
		int u = S.top();
		int v = next(u);
		if(v == t){
			return 1;
		}
		if(v != -1){
			if(color[v] == 0){
				color[v] = 1;
				S.push(v);
			}
		}
		else{
			S.pop();
			//color[u] = 1;
		}
	} 
	return 0; 
}
int main(){
	cin >> n >> m;
	for(i = 0; i < n; i++){
		color[i] = 0;
		for(j = 0; j < n; j++){
			M[i][j] = 0;
		}
	}
	for(i = 0; i < m; i++){
			cin >> s >> t;
			M[s][t] = M[t][s] = 1;
		
	}
	/*for(i = 0; i < n; i++){
		for(j = 0; j < n; j++){
			cout << M[i][j] << " ";
		}
		cout << endl;
	}*/
	cin >> q;
	for(i = 0; i < q; i++){
		cin >> s >> t;
		if(dfs(s, t)) 
			cout << "yes" << endl;
		else 
			cout << "no" << endl;
		for(j = 0; j < n; j++){
			color[j] = 0;
		}
	}
	
}

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

#define MAX 100000

std::vector<int> G[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 < G[cur].size(); ++i) {
            int t = G[cur][i];
            if (C[t]) continue;
            if (t == dest) return true;
            Q.push(t);
            C[t] = true;
        }
    }

    return false;
}

int main() {
    scanf("%d %d", &n, &m);

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

    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 <iostream>
#include <cstring>
#include <cstdlib>
#include <sstream>
#include <stack>
#include <queue>
#include <list>
#include <stdio.h>
#include <algorithm>
#define MAX 100000
using namespace std;
typedef long long ll;
#define MAX 100000
vector<int> g[MAX];
int col[MAX];
void dfs(int s,int color)
{
	int v;
	col[s]=color;
	for(int i=0;i<g[s].size();i++)
	{
		v=g[s][i];
		if(col[v]==-1){
			dfs(v,color);
		}
	}
}
void init(int n)
{
	int id=0;
	for(int i=0;i<n;i++)
	{
		if(col[i]==-1){
			dfs(i,++id);
		}
	}
}
int main()
{	
	int n,m,num;
	int s,k;
	cin>>n>>m;
	for(int i=0;i<m;i++)
	{
		cin>>s>>k;
		g[s].push_back(k);
		g[k].push_back(s);
	}
	for(int i=0;i<n;i++)
	{
		col[i]=-1;
	}
	init(n);
	cin>>num;
	while(num--)
	{
		cin>>s>>k;
		if(col[s]==col[k]) cout<<"yes"<<endl;
		else cout<<"no"<<endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int n, m;
vector< list<int> > v;
vector<bool> used;
int p[100000];
int r[100000];

int find(int x){
  if(p[x] == x) return x;
  else return p[x] = find(p[x]);
}
void unite(int x, int y){
  x = find(x);
  y = find(y);
  if(x == y) return;

  if(r[x] < r[y])
    p[x] = y;
  else{
    p[y] = x;
    if(r[x] == r[y]) r[x]++;
  }
}

bool same(int x, int y){
  return find(x) == find(y);
}

void dfs(int pos, int bgn){
  if(used[pos]) return;
  used[pos] = true;
  unite(pos, bgn);
  for(list<int>::iterator it = v[pos].begin(); it != v[pos].end(); it++){
    dfs(*it, bgn);
  }
}

int main(void){
  ios::sync_with_stdio(false);
  cin.tie(0);

  cin >> n >> m;
  v = vector< list<int> >(n, list<int>(0));
  used = vector<bool>(n, false);
  for(int i = 0; i < m; i++){
    int a, b; cin >> a >> b;
    v[a].push_back(b);
    v[b].push_back(a);
  }

  for(int i = 0; i < n; i++){
    p[i] = i;
    r[i] = 0;
  }

  for(int i = 0; i < n; i++){
    dfs(i, i);
  }

  int q; cin >> q;
  for(int i = 0; i < q; i++){
    int a, b;
    cin >> a >> b;
    if(same(a, b)) cout << "yes" << endl;
    else cout << "no" << endl;
  }
  return 0;
}

C++: #include <stdio.h>
#define rep(i, n) for(int i = 0; i < n; ++i)
 
int main(void) {
  int n, m;
  scanf("%d%d", &n, &m);
  int uf[n];
  rep(i, n) uf[i] = i;
  rep(i, m) {
    int s, t, nows, nowt;
    scanf("%d%d", &s, &t);
    nows = s, nowt = t;
    while(uf[nows] != nows) {
      nows = uf[nows];
    }
    while(uf[nowt] != nowt) {
      nowt = uf[nowt];
    }
    uf[nowt] = nows;
  }
  rep(i, n) {
    int nows = i;
    while(uf[nows] != nows) {
      nows = uf[nows];
    }
    uf[i] = nows;
  }
  /*rep(i, n) printf("%d ", uf[i]);
  printf("\n");*/
  int q;
  scanf("%d", &q);
  rep(i, q) {
    int s, t;
    scanf("%d%d", &s, &t);
    if(uf[s] != uf[t]) printf("no\n");
    else printf("yes\n");
  }
  return 0;
}