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 <cstdio>
#include <algorithm>
#include <vector>

using namespace std;

struct UnionFindTree {
    size_t n;
    vector<int> tree;
    UnionFindTree(size_t n): n(n) {
        tree = vector<int>(n, -1);
    }
    int find_root(size_t v) {
        if (tree[v] < 0) return v;
        return tree[v] = find_root(tree[v]);
    }
    bool unite(size_t x, size_t y) {
        x = find_root(x);
        y = find_root(y);
        if (x == y) return false;
        if (rank(x) < rank(y)) swap(x, y);
        tree[x] += tree[y];
        tree[y] = x;
        return true;
    }
    bool has_same_root(size_t x, size_t y) {
        return find_root(x) == find_root(y);
    }
    size_t rank(size_t v) {
        return -tree[find_root(v)];
    }
};

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

    UnionFindTree tree(n);
    for (size_t i=0; i<m; ++i) {
        size_t s, t;
        scanf("%zu %zu", &s, &t);

        tree.unite(s, t);
    }

    size_t q;
    scanf("%zu", &q);

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

        printf("%s\n", tree.has_same_root(s, t)? "yes":"no");
    }

    return 0;
}

C++: #include <bits/stdc++.h>
#include <sstream>
using namespace std;
int arr[100005];
int find(int index){
	while(1){
		if(arr[index]==-1)
			break;
		else
			index=arr[index];
	}
	return index;
}
int main(){
	ios::sync_with_stdio(0);cin.tie(0); 
	int n,m,a,b;
	cin >> n >> m;
	for(int i=0;i<=n;i++){
		arr[i]=-1;
	}
	while(m--){
		cin >> a >> b;
		int tmp1=find(a);
		int tmp2=find(b);
		if(tmp1!=tmp2){
			arr[tmp2]=tmp1;
		}
	}
	
	int q;
	cin >> q;
	while(q--){
		cin >> a >> b;
		if(find(a)==find(b)){
			cout << "yes" << endl;
		}
		else{
			cout << "no" << endl;
		}
 	}
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<stack>
#include<queue>
#include<algorithm>
#include<ctime>

void dfs(std::vector<std::vector<int> > &n) {
	int question;
	std::cin >> question;

	for (int i = 0; i < question; i++) {
		int from, to;
		std::cin >> from >> to;
		std::stack<int> s;
		std::vector<std::vector<int> > went(n.size(), std::vector<int>(n.size(), 0));
		s.push(from);
		bool flag = false;
		while (s.size() != 0 && flag == false){
			int num = s.top(); s.pop();
			for (size_t j = 0; j < n[num].size(); j++) {
				if (n[num][j] == to) {
					flag = true;
					break;
				}
				if (went[num][j] == 0) {
					s.push(n[num][j]);
					went[num][j] = 1;
				}
			}
		}
		if (flag) {
			std::cout << "yes" << std::endl;
		} else {
			std::cout << "no" << std::endl;
		}
	}
}

int main() {
	int people, relation;

	std::cin >> people >> relation;

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

	for (int i = 0; i < relation; i++) {
		int from, to;
		std::cin >> from >> to;
		n[from].push_back(to);
		n[to].push_back(from);
	}

	dfs(n);

	return 0;
}

C++: #include<iostream>
#include<vector>
#include<limits.h>
#include<stack>
#include<string>
using namespace std;

vector< vector<int> > L(100005);
int c[100005]={};

void dfs (int v, int marker){
	if(c[v]!=0){
		return;
	}
	c[v]=marker;
	for (int i=0;i<L[v].size();i++){
		dfs(L[v][i],marker);
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	int n,m,a,b,q,s,t;
	cin >> n >> m;
	
	for (int i=0;i<m;i++){
		cin >> a >> b;
		L[a].push_back(b);
	}
	
	int marker=1;
	for (int i=0;i<n;i++){
		if (c[i]==0){
			dfs(i,marker);
			marker++;
		}
	}
	
	
	cin >> q;
	int d[2][q];
	for (int i=0;i<q;i++){
		cin >> d[i][0];
		cin >> d[i][1]; 
	}
	for (int i=0;i<q;i++){
		if(c[d[i][0]]==c[d[i][1]]){
			cout << "yes" << endl;
		}else{
			cout << "no" << endl;
		}
	}
	
	out(c);
	return 0;
}

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

const int MAX = 100005;
const int NIL = -1;
int n;
vector<int> G[MAX];
int color[MAX];


void dfs(int r, int c) {
  color[r] = c;
  for (int u: G[r]) {
    if (color[u] == NIL) {
      dfs(u, c);
    }
  }
}

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);
  }
  int color_id {0};
  memset(color, NIL, sizeof color);
  for (int i = 0; i < n; i++) {
    if (color[i] == NIL) {
      dfs(i, color_id++);
    }
  }

  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 <assert.h>
using namespace std;
#define MAX_V 100000

int represent[MAX_V];
int status[MAX_V];

int findRepresent(int x)
{
    if (represent[x] == x) {
        return x;
    } else {
        represent[x] = findRepresent(represent[x]);
        return represent[x];
    }
}

void unite(int x, int y)
{
    x = findRepresent(x);
    y = findRepresent(y);
    if (x == y)
        return;
    if (status[x] < status[y])
        swap(x, y);
    assert(status[x] >= status[y]);
    represent[y] = x;
    if (status[x] == status[y])
        status[x]++;
}

bool same(int x, int y)
{
    return (findRepresent(x) == findRepresent(y));
}

int main()
{
    for (int i = 0; i < MAX_V; ++i) {
        represent[i] = i;
        status[i] = 0;
    }

    int n, m;
    cin >> n >> m;
    for (int i = 0; i < m; ++i) {
        int a, b;
        cin >> a >> b;
        unite(a, b);
    }
    int q;
    cin >> q;
    for (int i = 0; i < q; ++i) {
        int from, to;
        cin >> from >> to;
        cout << (same(from, to)? "yes" : "no") << '\n';
    }
    return 0;
}