Go: package main

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

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	nNodes := scanInt(sc)
	nConns := scanInt(sc)

	graph := make([][]int, nNodes)
	for i := 0; i < nConns; i++ {
		a, b := scanInt(sc), scanInt(sc)
		graph[a] = append(graph[a], b)
		graph[b] = append(graph[b], a)
	}

	groups := make([]int, nNodes)

	var setGroups func(int, int)
	setGroups = func(u int, groupId int) {
		if groups[u] > 0 {
			return
		}
		groups[u] = groupId

		for _, v := range graph[u] {
			setGroups(v, groupId)
		}
	}
	for i := 0; i < nNodes; i++ {
		setGroups(i, i+1)
	}

	nQuestions := scanInt(sc)

	w := bufio.NewWriter(os.Stdout)
	var ans string
	for i := 0; i < nQuestions; i++ {
		a, b := scanInt(sc), scanInt(sc)
		if groups[a] == groups[b] {
			ans = "yes"
		} else {
			ans = "no"
		}
		fmt.Fprintln(w, ans)
	}
	w.Flush()
}

func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

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

using namespace std;

class Relation{
public:
	Relation(int tmp_n,int tmp_m){
		n = tmp_n;
		m = tmp_m;
		V = new vector<int>[n];
		group = new int[n];
		for(int i=0;i<n;i++){
			group[i] = 0;
		}
		group_number = 1;
	}

	void push(int s,int t){
		V[s].push_back(t);
		V[t].push_back(s);
	}

	void makeGroup(){
		int node,i;
		queue<int> Q;
		Q.push(0);
		group[0] = 1;
		while(true){
			while(!Q.empty()){
				node = Q.front();
				Q.pop();
				if(V[node].size() > 0){
					for(int k=0; k < V[node].size();k++){
						if(group[V[node][k]] == 0){
							group[V[node][k]] = group[node];
							Q.push(V[node][k]);
						}
					}
				}
			}
			group_number++;
			for(i=0;i<n;i++){
				if(group[i] == 0){
					group[i] = group_number;
					Q.push(i);
					break;
				}
			}
			if(i == n) break;
		}
	}

	bool canAccsess(int s,int t){
		return group[s] == group[t];
	}

private:
	vector<int>* V;
	int* group;
	int group_number;
	int n,m;
};

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

	Relation relation(n,m);
	for(int i=0;i<m;i++){
		scanf("%d %d",&s,&t);
		relation.push(s,t);
	}
	relation.makeGroup();
	scanf("%d",&q);
	for(int i=0;i<q;i++){
		scanf("%d %d",&s,&t);
		if(relation.canAccsess(s,t)){
			printf("yes\n");
		}else{
			printf("no\n");
		}
	}
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
vector<vector<int>> G;
vector<int> C;
int color, n, m;

void dfs(int r) {
  C.at(r) = ++color;
  stack<int> S;
  S.push(r);
  while (S.size() > 0) {
    int u = S.top(); S.pop();
    rep(i, G.at(u).size()) {
      if (C.at(G.at(u).at(i)) == -1) {
        C.at(G.at(u).at(i)) = color;
        S.push(G.at(u).at(i));
      } 
    }
  }
}

void assing_color() {
  rep(i, n) {
    if (C.at(i) == -1){
      dfs(i);
    }
  }
}

int main() {
  cin >> n >> m;
  rep(i, n) G.push_back({});
  rep(i, n) C.push_back(-1);
  rep(i, m) {
    int a, b; cin >> a >> b;
    G.at(a).push_back(b);
    G.at(b).push_back(a);
  }
  assing_color();
  int q; cin >> q;
  rep(i, q) {
    int a, b; cin >> a >> b;
    if(C.at(a) == C.at(b)) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }
}

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

class Node{
private:
	int id;
	int friend_num;
	Node **friends;
	int check_id[2];
public:
	Node(int id, int n);
	~Node(){ delete[] friends; }
	void addFriend(Node *friend_node);
	bool searchFriend(int s_id, int t_id);
};

Node::Node(int id, int n)
{
	this->id = id;
	friend_num = 0;
	friends = new Node*[n];
	check_id[0] = check_id[1] = -1;
}

void Node::addFriend(Node *friend_node)
{
	friends[friend_num] = friend_node;
	friend_num++;
}

bool Node::searchFriend(int s_id, int t_id)
{
	if (check_id[0] == s_id && check_id[1] == t_id) return false;
	check_id[0] = s_id;
	check_id[1] = t_id;

	if (this->id == t_id) return true;

	for (int i = 0; i < friend_num; i++) {
		if (friends[i]->searchFriend(s_id, t_id)) return true;
	}

	return false;
}

int main(void)
{
	int n;
	cin >> n;	
	Node **node = new Node*[n];
	for (int i = 0; i < n; i++) node[i] = new Node(i, n);

	int m;
	cin >> m;
	for (int i = 0; i < m; i++) {
		int s, t;
		cin >> s >> t;
		node[s]->addFriend(node[t]);
		node[t]->addFriend(node[s]);
	}
		
	int q;
	cin >> q;
	for (int i = 0; i < q; i++) {
		int s, t;
		cin >> s >> t;
		bool result = node[s]->searchFriend(s, t);
		if (result) cout << "yes" << endl;
		else cout << "no" << endl;
	}

	delete[] node;
	return 0;
}

C++: #include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <stack>
#include <queue>


using namespace std;

int *passed;

bool do_check(int s, int t, vector< vector<int> > a){
  queue<int> q;
  
  bool flag = false;
  if(s==t){flag=true;}
  q.push(s);
  while(q.size()>0 && flag==false){
    s = q.front();
    q.pop();
    for(int i=0;i<a[s].size();i++){
      int tmp = a[s].at(i);
      if(tmp == t){
	flag = true;
      }
      if(passed[tmp] == 0){
	passed[tmp] = 1;
	q.push(tmp);
      }
    }
  }
  return flag;
}

int main(){
  int n, m;
  cin >> n >> m;
  passed = new int[n];
  vector< vector<int> > a;

  for(int i=0;i<n;i++){
    vector<int> tmp;
    a.push_back(tmp);
  }

  for(int i=0;i<m;i++){
    int tmpa, tmp;
    cin >> tmpa >> tmp;
    a[tmpa].push_back(tmp);
    a[tmp].push_back(tmpa);
  }

  // Questions
  int q_num;
  cin >> q_num;
  // cout << "q_num: " << q_num << endl;
  for(int i=0;i<q_num;i++){
    for(int j=0;j<n;j++){
      passed[j]=0;
    }
    int s, t;
    cin >> s >> t;

    // cout << s << ": " << do_check(s, t, a) << endl;
    if(do_check(s, t, a)){
      cout << "yes" << endl;
    }else{
      cout << "no" << endl;
    }
  }
  
}

C++: #include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<bitset>
#include<vector>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<iomanip>
#include <functional>
using namespace std;
typedef long long ll;
const int mod = 1000000007;
const int INF = 1 << 28;
//cout << fixed << std::setprecision(9)
//memset(a, 0, sizeof(a));
//--------------------------


int n, m, q;
vector<int> g[100005];
int col[100005];

void dfs(int r, int c)
{
	stack<int> stk;
	stk.push(r);
	col[r] = c;

	while (!stk.empty()) {
		int u = stk.top(); stk.pop();
		for (int i = 0; i < g[u].size(); i++) {
			int v = g[u][i];
			if (col[v] == -1) {
				stk.push(v);
				col[v] = c;
			}
		}

	}
}

void solve()
{
	int c = 0;

	for (int i = 0; i < n; i++) {
		col[i] = -1;
	}

	for (int i = 0; i < n; i++) {
		if (col[i] == -1) {
			dfs(i, ++c);
		}
	}
}


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

	return 0;
}