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>
#include <vector>
#include <stack>
#define MAX 100010
#define INFTY 10000000
#define NIL -1

using namespace std;

int N;
int M;
vector<int> V[MAX];
int color[MAX];

int dfs(int s, int t)
{
	stack<int> S;
	S.push(s);
	color[s] = t;
	
	while (!S.empty()) {
		int u = S.top(); S.pop();
		for (int i=0; i<V[u].size(); i++) {
			int v = V[u][i];
			if (color[v] == NIL) {
				color[v] = t;
				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 i, n, u, v;	
	scanf("%d %d", &N, &M);	
	for (i = 0; i < M; i++) {
		scanf("%d %d", &n, &v);
		V[n].push_back(v);
		V[v].push_back(n);
	}
	
	assignColor();
	
	int Q;
	scanf("%d", &Q);
	for (i = 0; i < Q; i++) {
		scanf("%d %d", &u, &v);
		/*
		if (dfs(u, v) == 1) {
			puts("yes");
		}
		else {
			puts("no");
		}*/
		if (color[u] == color[v]) {
			puts("yes");			
		}
		else {
			puts("no");
		}
	}

	return 0;
}

C++: #include "bits/stdc++.h"

using namespace std;

class UnionFind
{
    vector<int> par;

public:
    UnionFind(int n) : par(n, -1) {}

    int root(int x)
    {
        if (par[x] < 0)
            return x;
        else
            return par[x] = root(par[x]);
    }

    bool merge(int x, int y)
    {
        x = root(x);
        y = root(y);
        if (x == y)
            return false;
        if (par[x] > par[y])
            swap(x, y);
        par[x] += par[y];
        par[y] = x;
        return true;
    }

    int size(int x) { return -par[root(x)]; }
};

void solve()
{
    int n, m, q;
    cin >> n >> m;
    UnionFind uf(n);
    while (m--)
    {
        int s, t;
        cin >> s >> t;
        uf.merge(s, t);
    }
    cin >> q;
    while (q--)
    {
        int s, t;
        cin >> s >> t;
        if (uf.root(s) == uf.root(t))
        {
            cout << "yes\n";
        }
        else
        {
            cout << "no\n";
        }
    }
}

int main()
{
    solve();
    return 0;
}

C++: #include<iostream>
#include<climits>
#include<vector>
#include<list>
#include<functional>
#include<algorithm>
#include<string>
#include<cmath>
#include<complex>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<tuple>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) for(int i=0;i<(n);i++)
#define INF (int)1e9
#define INFL (ll)1e11
using namespace std;
typedef long long ll;
typedef pair<int, int> P;

void dfs(int s, vector<vector<int>> v, vector<int> &used) {
	used[s] = 1;
	int n = v.size();
	int k = v[s].size();
	REP(l, k) {
		int j = v[s][l];
		if (!used[j]) {
			dfs(j, v, used);
		}
	}
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int n, m;
	cin >> n >> m;
	vector<vector<int>> v(n);
	REP(i, m) {
		int s, t;
		cin >> s >> t;
		v[s].push_back(t);
		v[t].push_back(s);
	}
	int q;
	cin >> q;
	REP(i, q) {
		int s, t;
		cin >> s >> t;
		vector<int> used(n, 0);
		dfs(s, v, used);
		if (used[t]) cout << "yes\n";
		else cout << "no\n";
	}
	

	return 0;
}

C++: #include<cstdio>
#include<iostream>
#include<stack>
#include<vector>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#define _USE_MATH_DEFINES // M_PI????????????????????????
#include<math.h>
#include<queue>
#pragma warning(disable:4996)
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 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);
	}
}

int main(){
	int s, t, m, q;
	cin >> n >> m;

	for(int i=0; i<n; 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" << "\n";
		}else{
			cout << "no" << "\n";
		}
	}
	return 0;
}