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 <cassert>
#include <cstdio>
#include <algorithm>
#include <iostream>
#include <vector>
#include <list>

class TVertex
{
    int FIndex;
    int FCommuniyId;
    std::list<TVertex*> FList;

public:
    TVertex(int Index)
     : FIndex(Index), FCommuniyId(0)
    {}
    void AddPath(TVertex* Vertex)
    {
        FList.push_back(Vertex);
    }
    void SetCommunity(int CommunityId)
    {
        if(FCommuniyId) return;
        FCommuniyId = CommunityId;
        for(std::list<TVertex*>::iterator It = FList.begin(); It != FList.end(); ++It){
            TVertex* V = *It;
            V->SetCommunity(CommunityId);
        }
    }
    int CommunityId()const
    {
        return FCommuniyId;
    }
};
class TGraph
{
    std::vector<TVertex*> FTable;
    void Init(int n)
    {
        assert(n > 0);
        FTable.resize(n);
        for(int i = 0; i < n; ++i){
            FTable[i] = new TVertex(i);
        }
    }
public:
    TGraph(int n)
    {
        Init(n);
    }
    void MakeFriend(int s, int t)
    {
        assert(s < FTable.size());
        assert(t < FTable.size());
        FTable[s]->AddPath(FTable[t]);
        FTable[t]->AddPath(FTable[s]);
    }
    void SetCommunity()
    {
        for(std::size_t i = 0; i < FTable.size(); ++i){
            FTable[i]->SetCommunity(i+1);
        }
    }
    bool IsSameCommunity(int s, int t)const
    {
        assert(s < FTable.size());
        assert(t < FTable.size());
        return FTable[s]->CommunityId() == FTable[t]->CommunityId();
    }
};

int main()
{
    int n, m;
    std::scanf("%d %d", &n, &m);
    TGraph Graph(n);
    for(int i = 0; i < m; ++i){
        int s, t;
        std::scanf("%d %d", &s, &t);
        Graph.MakeFriend(s, t);
    }
    int q;
    std::scanf("%d", &q)
    Graph.SetCommunity();
    for(int i = 0; i < q; ++i){
        int s, t;
        std::scanf("%d %d", &s, &t);
        std::printf("%s\n", (Graph.IsSameCommunity(s, t) ? "yes" : "no"));
    }
    return 0;
    
}

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

vector<vector<int> >g;
int n,m,q,s,t;

vector<bool>visited;
vector<int>color;
void dfs(int s){
    for(int i=0;i<g[s].size();i++){
        if(color[g[s][i]]==-1){
            color[g[s][i]]=color[s];
            dfs(g[s][i]);
        }
    }
}
int main() {
    scanf("%d %d",&n,&m);
    g.resize(n);
    color.resize(n,-1);
    for(int i=0;i<m;i++){
        scanf("%d %d",&s,&t);
        g[s].push_back(t);
    }
    for(int i=0;i<n;i++){
        if(color[i]==-1){
            color[i]=i;
            dfs(i);
        }
    }
    scanf("%d",&q);
    for(int i=0;i<q;i++){
        scanf("%d %d",&s,&t);
        printf((color[s]==color[t]?"yes\n":"no\n"));
    }
    return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;
int main()
{
    int n, m, q;
    scanf("%d %d", &n, &m);
    vector<vector<int> > a(n, vector<int>(0));
    for (int i = 0, j, k; i < m; i++)
    {
        scanf("%d %d", &j, &k);
        a[j].push_back(k);
        a[k].push_back(j);
    }
    vector<int> vis(n, -1);
    for (int i = 0; i < n; i++)
    {
        
        if (vis[i] == -1)
        {
            stack<int> b;
            b.push(i);
            vis[i] = i;
            for (int t; !b.empty(); )
            {
                t = b.top();
                b.pop();
                for (int j = 0; j < a[t].size(); j++)
                {
                    
                    if (vis[a[t][j]] == -1)
                    {
                        vis[a[t][j]] = i;
                        b.push(a[t][j]);
                    }
                }
            }
        }
    }
    
    scanf("%d", &q);
    for (int i = 0, j, k; i < q; i++)
    {
        scanf("%d %d", &j, &k);
        printf(vis[j] == vis[k] ? "yes\n" : "no\n");
    }
}