Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

func newGraph(nNodes int) *Graph {
	g := Graph{}
	g.nodes = make([]*GraphNode, nNodes)
	for iNode := 0; iNode < len(g.nodes); iNode++ {
		g.nodes[iNode] = &GraphNode{}
		g.nodes[iNode].key = GraphNodeKey(iNode)
	}
	return &g
}

var infty = 1000000000

type GraphNodeKey int

// GraphNode is a node for undirected graph
type GraphNode struct {
	key       GraphNodeKey
	adjacents []*GraphNode
	visited   bool
	d, f      int
	parent    *GraphNode
	cc        int
}

func (g *Graph) setAdjacent(l, r GraphNodeKey) {
	g.nodes[l].adjacents = append(g.nodes[l].adjacents, g.nodes[r])
}

// Graph is a undirected graph
type Graph struct {
	nodes []*GraphNode
}

func (g *Graph) initialize() {
	for iNode := 0; iNode < len(g.nodes); iNode++ {
		g.nodes[iNode].visited = false
		g.nodes[iNode].d = infty
		g.nodes[iNode].f = infty
		g.nodes[iNode].parent = nil
		g.nodes[iNode].cc = -1 // 22.3-12
	}
}

type QueueEntry struct {
	node *GraphNode
	next *QueueEntry
}

type Queue struct {
	head, tail *QueueEntry
}

func (q *Queue) enqueue(node *GraphNode) {
	entry := QueueEntry{}
	entry.node = node

	if q.tail == nil {
		q.head = &entry
		q.tail = &entry
		return
	}

	q.tail.next = &entry
	q.tail = q.tail.next
}

func (q *Queue) dequeue() *QueueEntry {
	if q.head == nil {
		return nil
	}
	poped := q.head
	q.head = q.head.next
	if q.head == nil {
		q.tail = nil
	}
	return poped
}

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

var time = 0

func fillDistancesByDepthFirstSearch(g *Graph) {
	g.initialize()
	time = 0
	cc := 0

	for _, u := range g.nodes {
		if !u.visited {
			dfsVisit(g, u, cc)
			cc++
		}
	}
}

func dfsVisit(g *Graph, u *GraphNode, cc int) {
	time++
	u.d = time
	u.cc = cc

	u.visited = true
	for _, v := range u.adjacents {
		if !v.visited {
			v.parent = u
			dfsVisit(g, v, cc)
		}
	}
	time++
	u.f = time
}

func main() {
	scanner.Split(bufio.ScanWords)

	nUsers := nextInt()
	nEdges := nextInt()
	graph := newGraph(nUsers)
	for iEdge := 0; iEdge < nEdges; iEdge++ {
		l := GraphNodeKey(nextInt())
		r := GraphNodeKey(nextInt())
		graph.setAdjacent(l, r)
		graph.setAdjacent(r, l)
	}

	fillDistancesByDepthFirstSearch(graph)

	nQueries := nextInt()
	for iQuery := 0; iQuery < nQueries; iQuery++ {
		l := GraphNodeKey(nextInt())
		r := GraphNodeKey(nextInt())

		// fmt.Println(graph.nodes[l].d, graph.nodes[r].d, graph.nodes[r].f, graph.nodes[l].f)
		if graph.nodes[l].cc == graph.nodes[r].cc {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

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

const int MAX = 100000, white = 0;
int n, colors[MAX], color = 0;
vector<int> G[MAX];

void dfs(int v){
    colors[v] = color;
    for (int i = 0; i < G[v].size(); i++)
    {
        if (colors[G[v][i]] == white)
        {
            dfs(G[v][i]);
        }
    }
}

void classification(){
    for (int i = 0; i < n; i++)
    {
        if (colors[i] == white)
        {
            color++;
            dfs(i);
        }
    }
}

int main(){
    int m, q;
    cin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int s, t;
        cin >> s >> t;
        G[s].emplace_back(t);
        G[t].emplace_back(s);
    }
    classification();
    cin >> q;
    for (int i = 0; i < q; i++)
    {
        int s, t;
        cin >> s >> t;
        if (colors[s] == colors[t])
        {
            cout << "yes" << endl;
        }
        else
        {
            cout << "no" << endl;
        }
    }
    
}

C++: #include<iostream>
#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() {
    cin>>n>>m;
    g.resize(n);
    color.resize(n,-1);
    for(int i=0;i<m;i++){
        cin>>s>>t;
        g[s].push_back(t);
    }
    for(int i=0;i<n;i++){
        if(color[i]==-1){
            color[i]=i;
            dfs(i);
        }
    }
    cin>>q;
    for(int i=0;i<q;i++){
        cin>>s>>t;
        printf((color[s]==color[t]?"yes\n":"no\n"));
    }
    return 0;
}

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

using namespace std;

#define N_MAX 100000

int search_connection(int s, int t);
vector<int> G[N_MAX], check_v;

int main()
{
    int n, m, i, s, t, q;

    cin >> n >> m;

    //??£??\??????????????????
    for (i = 0; i < m; i++) {
        cin >> s >> t;
        G[s].push_back(t);
        G[t].push_back(s);
    }

    //??????????????????
    cin >> q;
    for (i = 0; i < q; i++) {
//        cout << "Q. " << i << endl;

        cin >> s >> t;

        if (check_v.size() != 0) check_v.clear();

        check_v.push_back(s);
        if ( search_connection(s, t) )
            cout << "yes" << endl;
        else
            cout << "no" << endl;
    }

    return 0;
}

int search_connection(int s, int t) {
    int i;
//    cout << "search " << s << ", " << t << endl;

    for (auto itr = G[s].begin(); itr != G[s].end(); itr++) {
        if (*itr == t) {
            return 1;
        }
        else if ( std::find(check_v.begin(), check_v.end(), *itr) != check_v.end() ) {
            //*itr?????¢?????¢?´¢??????node?????´??????????????¢?´¢????????????
        }
        else {
            //*itr???????????¢?´¢???????????????node?????´???
            check_v.push_back(*itr);
            if ( search_connection(*itr, t) )
                return 1;
        }
    }

    return 0;
}

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

using namespace std;

static const int N = 100;

int n, m;
int color[N], dist;

vector<int> G[N];

void dfs(int i, int c){
	queue<int> q; q.push(i);
	color[i] = c;

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


void search(){
	for (int i = 0; i < n; ++i) color[i] = -1;

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


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

	for (int i = 0; i < m; ++i) {
		int u, v; cin >> u >> v;
		G[u].push_back(v);
		G[v].push_back(u);
	}

	search();

	cin >> n;
	for (int i = 0; i < n; ++i)
	{
		int u, v; cin >> u >> v;
		if (color[u] == color[v]) cout << "yes" << endl;
		else cout << "no" << endl;
	}

	return 0;
}