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 <bits/stdc++.h>
using namespace std;
static const int MAX = 100000;
static const int NIL = -1;

int n, m;
vector<int> color(MAX, NIL);
vector<vector<int>> M(MAX);

void dfs(int i, int id) {
  int size = M[i].size();
  for (int j = 0; j < size; j++) {
    if (color[M[i][j]] == NIL) {
      color[M[i][j]] = id;
      dfs(M[i][j], id);
    }
  }
}

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

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

  for (int i = 0; i < m; i++) {
    int id, f;
    cin >> id >> f;
    M[id].push_back(f);
    M[f].push_back(id);
  }
  int qn;
  cin >> qn;
  vector<vector<int>> q(qn, vector<int>(2));
  for (int i = 0; i < qn; i++) {
    cin >> q[i][0] >> q[i][1];
  }

  assignColor();

  for (int i = 0; i < qn; i++) {
    if (color[q[i][0]] == color[q[i][1]]) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }
}

C++: #include<bits/stdc++.h>
using namespace std;
using UL = unsigned int;
using ULL = unsigned long long;
using LL = long long;
#define rep(i,n) for(UL i=0; i<(n); i++)

vector<UL> E[100000];
UL D[100000];

int main() {
 UL N,M; scanf("%u%u",&N,&M);
 rep(i,M){
  UL u,v; scanf("%u%u",&u,&v);
  E[u].push_back(v);
  E[v].push_back(u);
 }
 rep(i,N) D[i]=~0u;
 rep(s,N){
  if(D[s]!=~0u) continue;
  queue<UL> Q; Q.push(s); D[s]=s;
  while(Q.size()){
   UL p=Q.front(); Q.pop();
   for(UL e:E[p]){
    if(D[e]!=~0u) continue;
    D[e]=D[p];
    Q.push(e);
   }
  }
 }
 UL Q; scanf("%u",&Q);
 rep(q,Q){
  UL s,t; scanf("%u%u",&s,&t);
  if(D[s]==D[t]) printf("yes\n");
  else printf("no\n");
 }
 return 0;
}

C++: 
#include<stdio.h>
#define Num 100000
 
int a[Num];
int search(int c){
   if(c == a[c])
      return c;
   return a[c] = search(a[c]);
 }
int main(){
   int i,x,y,n,m,z;
   for(i=0;i<Num;i++){
      a[i] = i;
   }
   scanf("%d %d",&x,&y);
   for(i=0;i<y;i++){
      scanf("%d %d", &n,&m);
      if(search(n) != search(m)){
         a[search(m)] = search(n);
      }
   }
   scanf("%d",&z);
   for(i=0;i<z;i++){
      scanf("%d %d",&n,&m);
      if(search(n) == search(m))
         printf("yes\n");
      else
         printf("no\n");
   }
 
   return 0;
}

C++: #include <iostream>
#include <vector>
#include <stack>
using namespace std;
#define N 100000

int group[N],nt[N];
vector<int> vec[N];
int n,m;

int dfs_visit(int x,int k){
  stack<int> S;
  S.push(x);
  while(!S.empty()){
    int u=S.top();S.pop();
    for(int i=0;i<vec[u].size();i++){
      int v=vec[u][i];
      if(group[v]==0){
        group[v]=k;
        S.push(v);
      }
    }
  }
}
void dfs(){
  int id=1;
  for(int i=0;i<n;i++){
    if(group[i]==0) dfs_visit(i,id++);
  }
}
int main(){
  cin>>n>>m;
  for(int i=0;i<m;i++){
    int s,t;
    cin>>s>>t;
    vec[s].push_back(t);
    vec[t].push_back(s);
  }
  dfs();
  int q;
  cin>>q;
  for(int i=0;i<q;i++){
    int a,b;
    cin>>a>>b;
    if(group[a]==group[b]){
      cout<<"yes"<<"\n";
    }else{
      cout<<"no"<<"\n";
    }
  }
}

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

static const int MAX=100000;
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);
        }
      }
    }
}

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

  cin>>n>>m;

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

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

  cin>>q;

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

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

  return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <vector>
#include <set>
#include <string>
#include <queue>
#include <algorithm>
#include <map>
#include <cmath>
#include <list>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cstring>

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

using namespace std;

const int INF = 1 << 30;
const int MOD = 1000000007;
const int MAX = 100000;
const int N = 10000;

vector<int> G[MAX];
int T[MAX];
int A[N], B[N];

int find_next(int i, int n) {
	int ret = -1;
	for (int j = i; j < n; j++) {
		if (T[j]) continue;
		ret = j;
		break;
	}
	return ret;
}

int main() {
	int n, m; cin >> n >> m;
	rep(i, m) {
		int s, t; cin >> s >> t;
		G[s].push_back(t);
		G[t].push_back(s);
		T[i] = 0;
	}
	int q; cin >> q;
	rep(i, q) {
		int a, b; cin >> a >> b;
		A[i] = a; B[i] = b;
	}

	queue<int> Q;
	int next = 0, type = 0;
	while (true) {
		if (Q.empty()) {
			int i = find_next(next, n);
			if (i == -1) break;
			type++;
			T[i] = type;
			Q.push(i);
			continue;
		}
		int i = Q.front(); Q.pop();
		for (auto j : G[i]) {
			if (T[j]) continue;
			T[j] = type;
			Q.push(j);
		}
	}
	rep(i, q) {
		if (T[A[i]] == T[B[i]]) cout << "yes" << endl;
		else cout << "no" << endl;
	}
}