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>
#include<stack>

struct node {
	std::vector<int> relation;
};

void dfs(std::vector<node> &n) {
	int d[100000];

	std::stack<int> s;
	for (size_t i = 0; i < n.size(); i++) {
		s.push(i);
		for (int k = 0; k < 100000; k++) {
			d[k] = 0;
		}
		while (s.size() != 0) {
			int num = s.top(); s.pop();
			d[num] = 1;
			for (std::vector<int>::iterator it = n[num].relation.begin(); it != n[num].relation.end(); it++) {
				if (d[*it] == 1) {
					n[num].relation.erase(it);
					it--;
				} else {
					s.push(*it);
					d[*it] = 1;
				}
			}
		}
	}
}

bool isconnect(std::vector<node> n, int from, int to) {
	std::stack<int> s;
	s.push(from);
	while(s.size() != 0) {
		from = s.top(); s.pop();
		for (std::vector<int>::iterator it = n[from].relation.begin(); it != n[from].relation.end(); it++) {
			if (to == *it) return true;
			s.push(*it);
		}
	}
	return false;
}

int main() {
	int people, relation;
	
	std::cin >> people >> relation;

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

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

	dfs(n);

	int question;
	std::cin >> question;

	for (int i = 0; i < question; i++) {
		int from, to;
		std::cin >> from >> to;
		if (isconnect(n, from, to)) {
			std::cout << "yes" << std::endl;
		} else {
			std::cout << "no" << std::endl;
		}
	}

	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
const int N = 1000000;
int v[N]={0};

int main(){
	int n,m,q;
	cin >> n >> m;
	for(int i=0;i<n;i++){
		v[i]=i;
	}
	for(int i=0;i<m;i++){
		int k,l;
		cin >> k >> l;
		v[l]=v[k];
	}
	cin >> q;
	for(int i=0;i<q;i++){
		int k,l;
		cin >> k >> l;
		if(v[k]==v[l])cout << "yes" << endl;
		else cout << "no" << endl;
	}

    return 0;
}

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

struct UnionFind{
    vector<int> parent;
    UnionFind(int size): parent(size, -1) {}
    
    int root(int x){
        return parent[x]<0? x: parent[x] = root(parent[x]);
    }
    void uniteSet(int x, int y){
        x = root(x);
        y = root(y);
        if (x==y) return;
        if (parent[x]>parent[y]) swap(x,y);
        //parent[x] += parent[y];
        parent[y] = x;
    }
    bool findSet(int x, int y){
        return root(x) == root(y);
    }
};

int main(){cin.tie(0);ios::sync_with_stdio(false);
    
    int nb_v, nb_lines;
    cin >>nb_v
        >>nb_lines;
    UnionFind G(nb_v);
    for(int i=0; i<nb_lines; ++i){
        int v1, v2;
        cin >>v1
            >>v2;
        G.uniteSet(v1,v2);
    }

    cin >>nb_lines;
    for(int i=0; i<nb_lines; ++i){
        int v1, v2;
        cin >>v1
            >>v2;
        cout<<(G.findSet(v1, v2)? "yes\n":"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);
            }
            
        }
    }
        }

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 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;
    
}