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>
using namespace std;
  
int main() {
int d[100100];
int m,n,q;
cin>>n>>m;
for(int i=0;i<n;i++){
    d[i]=i;
}
for(int l=0;l<m;l++){
    int a,b;
    cin>>a>>b;
    int j ,h;
    j=a,h=b;
while(d[j]!=j && d[h]!=h){
    j=d[j];
    h=d[h];
}
if(d[j]==j){
	while(d[h]!=h){
		h=d[h];
	}
    d[j]=h;

    d[a]=h;
d[b]=h;
}
else{
	while(d[j]!=j){
		j=d[j];
	}
  d[h]=j;
    d[b]=j;
d[a]=j;
}
}
cin>>q;
for(int y=0;y<q;y++){
    int a,b;
    cin>>a>>b;
        int j ,h;
    j=a,h=b;
while(d[j]!=j && d[h]!=h){
    j=d[j];
    h=d[h];
}
if(d[j]==j){
	while(d[h]!=h){
		h=d[h];
	}}
else{
while(d[j]!=j){
		j=d[j];
	}
}

    if(j==h){
        cout<<"yes"<<endl;
    }
    else{
        cout<<"no"<<endl;
    }
}
    return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

#define REP(i, n) for(int i = 0; i < n; i++)

int n, m;
vector<int> G[100000];
int id[100001];
int visit[100001] = {0};
int s, t;

void check(int x, int u) {
    visit[x] = 1;
    id[x] = u;

    int v;
    REP(i, G[x].size()) {
        v = G[x][i];
        if (visit[v] == 0) check(v, u);
    }
}

int main() {
    cin >> n >> m;
    int a, b;
    REP(i, m) {
        cin >> a >> b;
        G[a].push_back(b);
        G[b].push_back(a);
    }

    REP(i, n) {
        if (visit[i] == 0) check(i, i);
    }

    int q;
    cin >> q;
    REP(i, q) {
        cin >> s >> t;
        if (id[s] == id[t]) {
            cout << "yes" << endl;
        } else {
            cout << "no" << endl;
        }
    }

    REP(i, n) {
        cout << id[i] << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <climits>
#include <cmath>
#include <algorithm>
#include <utility>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#define MAX 100000
#define INFTY 1<<30 // 2^30
using namespace std;
typedef long long llong;

static const int NIL = -1;

int n;
vector<int> G[MAX];
int color[MAX];

void dfs(int r, int c)
{
  stack<int> S;
  S.push(r);
  color[r] = c;
  while(!S.empty())
  {
    int u = S.top(); S.pop();
    for(int i = 0; i < G[u].size(); i++)
    {
      int v = G[u][i];
      if(color[v] == NIL)
      {
        color[v] = c;
        S.push(v);
      }
    }
  }
}

void assingColor()
{
  int id = 1;
  for(int i = 0; i < n; i++) color[i] = NIL;
  for(int u = 0; u < n; u++)
    if(color[u] == NIL) dfs(u,id++);
}

int main()
{
  int s, t, m ,q;
  cin >> n >> m;
  for(int i = 0; i < m; i++)
  {
    cin >> s >> t;
    G[s].push_back(t);
    G[t].push_back(s);
  }

  assingColor();

  cin >> q;
  for(int i = 0; i < q; i++)
  {
    cin >> s >> t;
    cout << ((color[s] == color[t]) ? "yes" : "no") << endl;
  }
  return 0;
}

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

static const int MAX = 100000;
static const int WHITE = 0;
//static const int BLACK = 1;

vector<int> V[MAX];
//int n;
int color[MAX] = {0};

void dfs(int u,int c)
{
	stack<int> S;
	S.push(u);
	color[u] = c;
	while(!S.empty())
	{
		int v = S.top();
		S.pop();
		for(int i=0; i<V[v].size(); i++)
		{
			int k = V[v][i];
			if(color[k] == WHITE)
			{
				S.push(k);
				color[k] = c;
			}

		}
	}
}

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

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

	int q;
	scanf("%d", &q);
	for(int i=0; i<q; i++)
	{
		scanf("%d%d",&u,&v);
		if(color[u] == color[v])
			printf("yes\n");
		else
			printf("no\n");
	}

	return 0;
}

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

using namespace std;

#define GRAPH_SIZE 100000

enum state_t {
  WHITE,
  GRAY,
  BLACK,
};

struct vertex_t {
  uint32_t color;
  vector<uint32_t> connections;
};

static vertex_t graph[GRAPH_SIZE];
static state_t state[GRAPH_SIZE];

static void colorize(uint32_t index, uint32_t color)
{
  if (state[index] == WHITE) {
    state[index] = GRAY;
    graph[index].color = color;
    for (uint32_t i = 0; i < graph[index].connections.size(); i++) {
      colorize(graph[index].connections[i], color);
    }
    state[index] = BLACK;
  }
}

void check_connection(size_t num)
{
  for (uint32_t i = 0; i < num; i++) {
    state[i] = WHITE;
  }

  uint32_t color = 1;
  for (uint32_t i = 0; i < knum; i++) {
    colorize(i, color);
    color++;
  }
}

#include <iostream>

int32_t main()
{
  uint32_t n, m;
  cin >> n >> m;

  for (uint32_t i = 0; i < m; i++) {
    uint32_t index, to;
    cin >> index >> to;
    graph[index].connections.push_back(to);
  }

  check_connection(n);

  uint32_t qs;
  cin >> qs;

  for (uint32_t i = 0; i < qs; i++) {
    uint32_t from, to;
    cin >> from >> to;

    if (graph[from].color == graph[to].color) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }

  return 0;
}