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

void divide(vector<vector<int>> v, vector<int> &used) {
	int s = 0;
	int group = 1;
	int n = v.size();
	while (s < n) {
		dfs(s, group++, v, used);
		while (s < n && used[s]) s++;
	}
}

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

	return 0;
}

C++: #include <iostream>
#include <sstream>
#include <cstdio>
#include <stdlib.h>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
#define max 100000
vector<int> vn[max];
int grp[max];
int n;

void grouping(int g,int cnt){
  if(grp[g]!=0)return;
  grp[g]=cnt;
  for(int i=0;i<(int)vn[g].size();i++)
    grouping(vn[g][i],cnt);
}

int main(){
  int m,t,u,cnt;
  cin>>n>>m;
  for(int i=0;i<m;i++){
    cin>>t>>u;
    vn[t].push_back(u);
    vn[u].push_back(t);
  }
  cnt=1;
  for(int i=0;i<n;i++){
    if(grp[i]!=0)continue;
    grouping(i,cnt);
    cnt++;
  }
  //for(int i=0;i<n;i++)cout<<"i: "<<i<<"grp "<<grp[i]<<endl;
  cin>>m;
  for(int i=0;i<m;i++){
    cin>>t>>u;
    if(grp[t]==grp[u]&&grp[t]!=0)cout<<"yes"<<endl;
    else cout<<"no"<<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <vector>
#define N_MAX 100000
using namespace std;

vector<int> sns[N_MAX];
int* group;
int g = 0;

void dfs(int s) {
  if (group[s] != 0) return;
  group[s] = g;
  
  int len = sns[s].size();
  for (int i = 0; i < len; i++) {
    dfs(sns[s][i]);
  }
}

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

  for (int i = 0; i < m; i++) {
    cin >> s >> t;

    sns[s].push_back(t);
    sns[t].push_back(s);
  }

  // dfs
  group = new int[n];
  for (int i = 0; i < n; i++) {
    if (group[i] == 0) {
      g++;
      dfs(i);
    }
  }

  cin >> q;
  for (int i = 0; i < q; i++) {
    cin >> s >> t;
    if (group[s] == group[t]) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using msi = map<string, int>;
using mii = map<int, int>;
using psi = pair<string, int>;
using pii = pair<int, int>;
using vlai = valarray<int>;
#define rep(i,n) for(int i=0;i<n;i++)
#define range(i,s,n) for(int i=s;i<n;i++)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define fs first
#define sc second
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define INF 1E9
#define EPS 1E-9
#define MOD (1E9+7)
#define PI 3.1415926535897932384

std::ostream &operator<<(std::ostream &out, const vector<int> &tgt)
{
	string s;
	for (int i = 0; i<tgt.size(); i++) {
		s += (to_string(tgt[i]) + ((i != tgt.size() - 1) ? " " : ""));
	}
	out << s;
	return out;
}

vi rnk,par;

int find(int x){
	if (par[x] == x) return x;
	return par[x] = find(par[x]);
}

void unite(int x, int y) {
	x = find(x);
	y = find(y);
	if (x == y)return;
	if (rnk[x] < rnk[y]) {
		par[x] = y;
	}
	else {
		par[y] = x;
		if (rnk[x] == rnk[y])rnk[x]++;
	}
}

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

int main() {
	int n,m,a,b,q;
	cin >> n >> m;
	par.resize(n);
	rnk.resize(n);
	rep(i, n) {
		par[i] = i;
		rnk[i] = 0;
	}

	rep(i, m) {
		cin >> a >> b;
		unite(a, b);
	}
	cin >> q;
	rep(i, q) {
		cin >> a >> b;
		cout << (same(a, b) ? "yes" : "no") << endl;
	}

}

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

const int MAX = 100000;
const int NIL = -1;

int n;
std::vector<int> G[MAX];
int state[MAX];

void dfs(int u, int id) {
  	
	stack<int> S;
	S.push(u);
	state[u] = id;
	
	while( !S.empty() ) {
		int t = S.top();S.pop();
		for( int i = 0; i < G[t].size(); i++ ) {
			int v = G[t][i];
			if(state[v] == NIL ) {
				state[v] = id;
			    S.push(v);
		    }
		}
		
	}	

}

void assignState(){
	int id = 1;
	for(int i = 0; i < n; i++ ) state[i] = -1;
	for(int u = 0; u < n; u++ ) {
		if( state[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);
    }
    
    assignState();

    cin >> q;

    for( int i = 0; i < q; i++ ){
    	cin >> s >> t;
    	if( state[s] == state[t] ) cout << "yes" << endl;
    	else cout << "no" << endl;
    }

    return 0;
}