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>
#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;
	}
}

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

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);
            }
        }
    }
}

void assign_color()
{
    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);
    }
    assign_color();
    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;
}