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<iostream>
#include<vector>
 
using namespace std;
 
int main(){
    int n, m, s, t, q, i, j;
    int id, color = 0;
    bool answer_yes = false;
 
    // enter
    cin >> n >> m;
    vector< vector<int> > Adj(n);
    vector<int> Stack;
    vector<int> Check(n, 0);
    vector<int>::iterator it, itend;
    for (i = 0; i < m; i++) {
        cin >> s >> t;
        Adj[s].push_back(t);
        Adj[t].push_back(s);
    }
    /*for (i = 0; i < n; i++) {
        cout << "\n" << i << " : " << flush;
        for (auto it2 = Adj[i].begin(); it2 != Adj[i].end(); it2++) {
            cout << *it2 << " " << flush;
        }
    }
    cout << endl;*/
 
    // calculate
    for (i = 0; i < n; i++) {
        if (Check[i] == 0) {
            color++;
            Stack.push_back(i);
            Check[i] = color;
            while (!Stack.empty()) {
                id = Stack.back();
                //cout << "\nid : " << id << " color : " << color << endl;
                itend = Adj[id].end();
                for (it = Adj[id].begin(); it != itend; it++) {
                    if (!Check[*it]) {
                        Stack.push_back(*it);
                        Check[*it] = color;
                        break;
                    }
                }
                if (it == itend) {
                    Stack.pop_back();
                }
            }
        }
    }
 
    //find
    cin >> q;
    for (i = 0; i < q; i++) {
        cin >> s >> t;      
        if (Check[s] == Check[t]) {
            cout << "yes" << endl;
        } else {
            cout << "no" << endl;
        }
    }
     
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
const int N = 1000000;
const int CRL = -1;
int v[N]={0};
void ketugou(int k,int l,int n){
	int x,mn;
	x = max(v[k],v[l]);
	mn = min(v[k],v[l]);
	for(int i=0;i<n;i++){
		if(v[i]==x)v[i]=mn;
	}
}

int main(){
	int n,m,q;
	memset(v, CRL, sizeof(v));
	cin >> n >> m;
	for(int i=0;i<m;i++){
		int k,l;
		cin >> k >> l;
		if(v[k]==CRL && v[l]==CRL){
			v[k] = v[l] = min(k,l);
		}else if(v[k]!=CRL && v[l]!=CRL){
			ketugou(k,l,n);
		}else if(v[k]==CRL){
			v[k]=v[l];
		}else{
			v[l]=v[k];
		}
	}
	cin >> q;
	for(int i=0;i<q;i++){
		int k,l;
		cin >> k >> l;
		if(v[k]==CRL || v[l]==CRL) cout << "no" << endl;
		else if(v[k]==v[l])cout << "yes" << endl;
		else cout << "no" << endl;
	}
    return 0;
}

C++: #include <iostream>
#include <cstdio>
#define MAX 100000

using namespace std;

int main(){
  int a[MAX]={};
  int n,m; cin>>n>>m;
  int s,t;
  int group=1;
  for(int i=0;i<m;i++){
    cin>>s>>t;
    if(a[s]==0 && a[t]==0){
      a[s]=a[t]=group;
      group++;
    }else if(a[s]==0){
      a[s]=a[t];
    }else if(a[t]==0){
      a[t]=a[s];
    }else{
      int tmp=a[t];
      a[t]=a[s];
      for(int j=0;j<n;j++){
        if(a[j]==tmp) a[j]=a[s];
      }
    }
  }

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

}

C++: #include <iostream>
#include "vector"
#include "stack"
using namespace std;
static const int mx=100000;
static const int nil=-1;

int n;
vector<int>g[mx];
int color[mx];

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 assigncolor()
{
	int id=1;
	for(int i=0;i<n;i++)color[i]=nil;
	for(int i=0;i<n;i++)
		if(color[i]==nil)dfs(i,id++);
}
int main(int argc, char *argv[]) {
	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);
	}
	
	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;
}

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

const int M = 10000000;

void connected_components(
  std::vector<std::vector<int> >& adj_list,
  std::vector<int>& component_numbers,
  int root, int current_component){
  assert(component_numbers[root] == M);

  std::queue<int> target_q;
  target_q.push(root);
  component_numbers[root] = current_component;
  // dist_q.push(0;)
  while(!target_q.empty()){
    int vtx = target_q.front(); target_q.pop();
    for(int const&  u : adj_list[vtx]){
      if(component_numbers[u] == M){
        target_q.push(u);
        component_numbers[u] = current_component;
      }
    }
  }
}

int main(int argc, char const *argv[]) {
  int n, m, q;
  std::cin >> n;
  std::cin >> m;

  std::vector<std::vector<int> > adj_list(n);

  for (size_t i = 0; i < m; i++) {
    int a, b;
    std::cin >> a;
    std::cin >> b;
    adj_list[a].push_back(b);
  }

  std::vector<int> component(n, M);

  for (size_t i = 0; i < n; i++) {
    if(component[i] == M){
      connected_components(adj_list, component, i, i);
    }
  }

  std::cin >> q;
  for(size_t i =0; i < q; i++){
    int a, b;
    std::cin >> a;
    std::cin >> b;
    bool in_same_component = (component[a] == component[b]);
    std::cout << (in_same_component ? "yes" : "no") << std::endl;
  }
  

  return 0;
}