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 <cstdio>
#include <cstdlib>
#include <cassert>
#include <string>
#include <cstring>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>

using namespace std;

// ---------------------
// repetition
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)

// debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

// ---------------------
#define INF 922337203685477580
typedef long long ll;
vector<int> par;

void init(int n) {
  par = vector<int>(n);
  REP(i, n) {
    par[i] = i;
  }
}
int root(int key) {
  if (par[key] == key) return key;
  return root(par[key]);
}
int same(int a, int b) {
  return root(a) == root(b);
}
void unite(int a, int b) {
  int x = root(a);
  int y = root(b);

  if (x == y) return;

  par[x] = y;
}

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

  init(n);

  REP(_, m) {
    int a, b;
    // cin >> a >> b;
    scanf("%d %d", &a, &b);
    unite(a, b);
  }
  int q;
  cin >> q;
  REP(_, q) {
    int a, b;
    // cin >> a >> b;
    scanf("%d %d", &a, &b);
    if (same(a, b)) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }

  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

#define NIL -1

typedef vector<int> Adj_list;
typedef vector<Adj_list> Adj_lists;
typedef vector<int> Group_ids;

void set_group_ids(const Adj_lists& adj_lists, Group_ids& group_ids){

  int id = -1;
  for(int i=0; i<adj_lists.size(); i++){
    if(group_ids.at(i) != NIL) continue;
    else id++;

    queue<int> q;
    q.push(i);

    while(!q.empty()){
      // visit top of queue
      const int& visit = q.front();
      const Adj_list& adj_list = adj_lists.at(visit);

      // push adjecent node which is not visited yet
      for(const int& adj : adj_list){
        if(group_ids.at(adj) == NIL){
          q.push(adj);
        }
      }

      group_ids.at(visit) = id;
      q.pop();
    }
  }
}

int main(){

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

  Adj_lists adj_lists(n);
  for(int i=0; i<m; i++){
    int a, b;
    scanf("%d %d", &a, &b);
    adj_lists.at(a).push_back(b);
    adj_lists.at(b).push_back(a);
  }

  Group_ids group_ids(n+1, NIL);
  set_group_ids(adj_lists, group_ids);

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

  return 0;
}

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

#define REP(i, n) for(int i=0;i<(int)(n);i++)
#define ALL(x) (x).begin(),(x).end()
const int INF = 1e9;

using namespace std;
int n, m;
struct node {
    int parent;
    vector<int> child;
};

int main() {
    cin >> n >> m;
    node person[n];
    REP(i, n)
        person[i].parent = -1;
    REP(i, m){
        int s, t;
        cin >> s >> t;
        if(person[s].parent == -1 && person[t].parent == -1){
            person[s].parent = s;
            person[t].parent = s;
            person[s].child.push_back(t);
        } else if(person[s].parent == -1){
            person[s].parent = person[t].parent;
            person[person[t].parent].child.push_back(s);
        } else if(person[t].parent == -1){
            person[t].parent = person[s].parent;
            person[person[s].parent].child.push_back(t);
        } else {
            REP(j, person[person[t].parent].child.size())
                person[person[person[t].parent].child[j]].parent = person[s].parent;
            int sz = person[person[t].parent].child.size();
            REP(j, sz)
                person[person[s].parent].child.push_back(person[person[t].parent].child[j]);
            person[person[t].parent].child.clear();
        }
    }
    int q;
    cin >> q;
    REP(i, q){
        int s, t;
        cin >> s >> t;
        if(person[s].parent != -1 && person[t].parent != -1  && person[s].parent == person[t].parent)
            cout << "yes" << endl;
        else
            cout << "no" << endl;
    }
    return 0;
}

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[N];

void dfs(int r, int c) {
  stack<int> S;
  S.push(s);
  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 u = 0; u < n; u++) {
    if (color[u] == NIL) {
      dfs(u, id++);
    }
  }
}

int main() {
  int m, 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();

  int q;
  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;
}