Go: package main

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

const MAX = 100000

type Queue struct {
	head      int
	tail      int
	container [MAX]int
}

func (q *Queue) push(n int) {
	q.container[q.tail] = n
	q.tail = (q.tail + 1) % MAX
}

func (q *Queue) pop() int {
	res := q.container[q.head]
	q.head = (q.head + 1) % MAX
	return res
}

func (q *Queue) isEmpty() bool {
	return q.head == q.tail
}

var sc = bufio.NewScanner(os.Stdin)
var route [][]int
var SEEN [MAX]bool
var GROUP [MAX]int

func scanInt() int {
	num, _ := strconv.Atoi(scanString())
	return num
}

func scanString() string {
	sc.Scan()
	return sc.Text()
}

func init() {
	sc.Split(bufio.ScanWords)
}

func bfs(start, group int) {
	que := Queue{}
	que.push(start)

	for !que.isEmpty() {
		id := que.pop()

		if SEEN[id] {
			continue
		}
		SEEN[id] = true
		GROUP[id] = group

		for _, next := range route[id] {
			que.push(next)
		}
	}
}

func main() {
	n, m := scanInt(), scanInt()
	route = make([][]int, n)
	for i := 0; i < m; i++ {
		s, t := scanInt(), scanInt()
		route[s] = append(route[s], t)
		route[t] = append(route[t], s)
	}

	for i := 0; i < n; i++ {
		if !SEEN[i] {
			bfs(i, i+1)
		}
	}

	w := bufio.NewWriter(os.Stdout)
	q := scanInt()
	for i := 0; i < q; i++ {
		s, t := scanInt(), scanInt()
		if GROUP[s] == GROUP[t] {
			fmt.Fprintln(w, "yes")
		} else {
			fmt.Fprintln(w, "no")
		}
	}
	w.Flush()
}

C++: /**
 */

/*
 * test case 1
 2 1 1 2 1 1 2  
 test case 2
 4 4 1 2 1 3 2 4 3 4 1 1 2   
 */


#include <iostream>
#include <vector>
#include <queue>
using namespace std;
vector< vector<int> > rel;
vector<bool> visited;
int n, m, q;
int dest = 0;


bool fre1(int j) 
{
	for (int i=0;i<rel[j].size();i++)
	{
		int kk = rel[j][i];
		if (kk==dest) return true;
		if (visited[kk])continue;
		visited[kk]=true;
		if(fre1(kk))return true;
	}
	return false;
}

/**
 * preserve a priority que of nodes with the most connections. 
 * if there is a node with only 2 connections go look for the other one.
 */

priority_queue< pair<int, int> > pq;


bool fre3(int start) 
{
	for (int i=0;i<rel[start].size();i++)
	{
		int cand = rel[start][i];
		if (cand==dest) return true;
		if (visited[cand])continue;
		visited[cand]=true;
		int point = rel[cand].size();
		if (point == 1) continue;
		if (point == 2) {
			if (fre3(cand)) return true;
		} else {
			pq.push(pair<int, int>(point, cand));
		}
	}
	return false;
}


bool fre2(int start) 
{
	pq.push(pair<int,int>(0, start));
	while (pq.size())
	{
		pair<int, int> p = pq.top();
		pq.pop();
		start = p.second;
		if (fre3(start)) return true;
	}
	return false;
}


int main()
{
	cin >> n;
	rel.resize(n);
	cin >> m;
	for (int i=1;i<=m;i++){
		int j, k;
		cin >> j >> k;
		rel[j].push_back(k);
		rel[k].push_back(j);
	}

	cin >> q;
	for (int i=1;i<=q;i++){
		int start;
		cin >> start >> dest;
		visited.clear();
		visited.resize(n, false);
		cout << (fre2(start) ? "yes" : "no") << endl;
		while (pq.size()) pq.pop(); // forgot this.
	}

	return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
#include <math.h>
#include<cstring>
#include <cstdio>
using namespace std;
typedef long long int ll;
#define rep(i, a, n) for (ll i = a; i < (ll)(n); i++)
long long GCD(long long a, long long b) { return b ? GCD(b, a%b) : a; }
long long LCM(long long a, long long b)  {return a/GCD(a,b)*b;}
int n,m,q;
int st,en;
vector<int> G[100000];
int color[100000];
int cnt=0;
void dfs(int st,int cnt)
{
    color[st]=cnt;
    for(int i=0;i<G[st].size();i++)
    {
        if(color[G[st][i]]==-1)
        {
            dfs(G[st][i],cnt);
        }
    }
}
void makeColor()
{
    for(int i=0;i<n;i++)
    {
        if(color[i]==-1)
        {
            dfs(i,++cnt);
        }
    }
}
int main(){
    memset(color,-1,sizeof(color));
    cin>>n>>m;
    for(int i=0;i<m;i++)
    {
        int a,b;
        cin>>a>>b;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    makeColor();
    cin>>q;
    
    for(int i=0;i<q;i++)
    {
        cin>>st>>en;
        if(color[st]==color[en])
            cout<<"yes"<<endl;
        else
            cout<<"no"<<endl;
    }
   return 0;
}

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

map<int, vector<int>> A;
int color[100001];

void assignColor(int u, int currentColor) {
    queue<int> Q;
    Q.push(u);
    color[u] = currentColor;
    int current;
    while(!Q.empty()) {
        current = Q.front();
        Q.pop();
        vector<int>::iterator it = A[current].begin();
        while(it != A[current].end()) {
            if (color[*it] == 0) {
                Q.push(*it);
                color[*it] = currentColor;
            }
            it++;
        }
    }
}

int main() {
    int n, m;
    cin >> n >> m;

    int u1, u2;
    for (int i = 0; i < m; i++) {
        cin >> u1 >> u2;
        A[u1].push_back(u2);
        A[u2].push_back(u1);
    }

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

    int c = 1;
    for (int i = 0; i < n; i++) {
        if (color[i] == 0) {
            assignColor(i, c);
            c++;
        }
    }

    int q, start, target;
    cin >> q;
    for (int i = 0; i < q; i++) {
        cin >> start >> target;

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

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

#define N 100000
#define WHITE 0  // 未訪問
#define BLACK 1  // 訪問ずみ

// 連結成分の番号を振る関数
void dfs(int n, int comp[], vector<int> G[]) {
  int i, j, vertex, neighbor, color[N];
  stack<int> S;
  // 初期状態
  for (i = 0; i < n; i++) color[i] = WHITE;

  for (i = 0; i < n; i++) {
    if (color[i] == WHITE) {
      // dfs
      S.push(i);
      while (!S.empty()) {
        vertex = S.top();
        S.pop();        
        color[vertex] = BLACK;  // 訪問済みにする
        comp[vertex] = i;  // 連結成分の番号を振る          
        for (j = 0; j < (int) G[vertex].size(); j++) {
          neighbor = G[vertex][j]; // 隣接している頂点：友人
          if (color[neighbor] == WHITE) S.push(neighbor);
        }
      }
    }
  }
}

int main() {
  int i, n, m, q, s, t;
  int comp[N];  // 連結成分の番号
  vector<int> G[N];  // グラフを表現する隣接リスト

  cin >> n >> m;
  // 隣接リストを作成
  for (i = 0; i < m; i++) {
    cin >> s >> t;
    G[s].push_back(t);
    G[t].push_back(s);
  }

  // グラフを連結成分に分ける
  dfs(n, comp, G);

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