Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N, M := sc.nextInt(), sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < M; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	group := make([]int, N)
	for i := 0; i < N; i++ {
		group[i] = -1
	}
	var dfs func(cur int)
	dfs = func(cur int) {
		for i := 0; i < len(G[cur]); i++ {
			next := G[cur][i]
			if group[next] == -1 {
				group[next] = group[cur]
				dfs(next)
			}
		}
	}
	num := 0
	for i := 0; i < N; i++ {
		if group[i] == -1 {
			group[i] = num
			dfs(i)
			num++
		}
	}

	Q := sc.nextInt()
	for i := 0; i < Q; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		if group[s] == group[t] {
			fmt.Fprintln(wtr, "yes")
		} else {
			fmt.Fprintln(wtr, "no")
		}
	}
	wtr.Flush()
}

C++: #include <stdio.h>
#include <vector>
#include <queue>
#define NUM 100000
#define NIL -1
using namespace std;

int node_num;
vector<int> v[NUM + 1];
queue<int> Q;
int color[NUM + 1];

bool is_connected(int a, int b){
    if(color[a] == color[b]){
        return true;
    }else{
        return false;
    }
}

void add_next(int n){
    for(int i = 0; i < v[n].size(); i++){
        if(color[v[n][i]] != NIL)
            continue;
        Q.push(v[n][i]);
        color[v[n][i]] = color[n];
    }
}

void bfs(){
    for(int i = 1; i <= node_num; i++){
        if(color[i] != NIL)
            continue;
        color[i] = i;
        Q.push(i);
        add_next(i);

        while(Q.size()){
            int top = Q.front();
            Q.pop();
            add_next(top);
        }
    }
    return;
}

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

int main(void){
    init();

    int m;
    scanf("%d", &node_num);
    scanf("%d", &m);

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

    bfs();
     
    int q;
    scanf("%d", &q);
    for(int i = 0; i < q; i++){
        int a, b;
        scanf("%d %d", &a, &b);
        if(is_connected(a, b)){
            printf("yes\n");
        }else{
            printf("no\n");
        }
    }
}

C++: #include <iostream>
#include <map>
#include <queue>
using namespace std;
int main(){

  int n,m,t1,t2;
  map <int,bool> g[100000];
  cin>>n>>m;
  for(int i=0;i<m;i++){
    cin>>t1>>t2;
    g[t1][t2]=1;
    g[t2][t1]=1;
  }
  int l;
  cin>>l;
  for(int i=0;i<l;i++){
    queue <int> q;
    bool f[100000]={1},find=false;
    cin>>t1>>t2;
    q.push(t1);
    for(;!q.empty();){
      for(int j=0;j<n;j++) if(g[q.front()][j]&&!f[j]){
          if(j==t2) find=true;
          f[j]=true;
          q.push(j);
	}
      q.pop();
      if(find) break;
    }
    if(find) cout<<"yes"<<endl;
    else cout<<"no"<<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <vector>
#include <stack>
using namespace std;
static const int MAX_N = 100010;
static const int NIL = -1;

vector<int> G[MAX_N];
int color[MAX_N];

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

int main() {
  int n, 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;
  }

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

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

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

const int NMAX = 100000;
const int MMAX = 100000;

vector<int> table[NMAX]; 

int color[NMAX];

void search(int s, int id, int n) {
	queue<int> q;
	q.push(s);
	color[s] = id;

	while(true) {
		if (q.empty()) {
			return;
		}
		int current = q.front(); q.pop();
		for (int i = 0; i < table[current].size(); i++) {
			int v = table[current][i];
			if (color[v] == -1) {
				q.push(v);
				color[v] = id;
			}
		}
	}
}

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

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

	for (int i = 0; i < m; i++) {
		int s, t;
		scanf("%d %d", &s, &t);
		table[s].push_back(t);
		table[t].push_back(s);
	}

	assignColor(n);

	int q;
	scanf("%d", &q);

	for (int i = 0; i < q; i++) {
		int s, t;
		scanf("%d %d", &s, &t);

		bool result = color[s] == color[t];
		if (result) {
			printf("yes\n");
		} else {
			printf("no\n");
		}
	}

	return 0;
}

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

const int N=100001;

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

void dfs(int x,int y){
  stack<int> S;
  
  S.push(x);
  color[x]=y;
  
  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]==-1){
	color[v]=y;
	S.push(v);
      }
    }
  }
}

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

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

  cin>>n>>m;

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

  assignColor();

  cin>>q;

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