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 <iostream>
#include <stack>
#include <vector>

using namespace std;

int NIL = -1;
const int MAX = 100000;
vector<int> SNS[MAX];
int color[MAX];

void dfs(int v, int colorIdx) {

	stack<int> S;
	S.push(v);
	color[v] = colorIdx;

	while (!S.empty()) {
		int s = S.top();
		S.pop();
		for (int i = 0; i < (int) SNS[s].size(); ++i) {
			int r = SNS[s][i];
			if (color[r] == NIL) {
				S.push(r);
				color[r] = colorIdx;
			}
		}
	}
}

void makeColor(int color[], int n) {
	int colorIdx = 0;
	for (int i = 0; i < n; ++i) {
		if (color[i] == NIL)
			dfs(i, colorIdx++);
	}
}

int main() {

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

	for (int i = 0; i < m; ++i) {
		int s, t;
		scanf("%d %d", &s, &t);
		SNS[s].push_back(t);
		SNS[t].push_back(s);
	}

	for (int i = 0; i < n; ++i)
		color[i] = NIL;

	makeColor(color, n);

	int q;
	scanf("%d", &q);
	for (int i = 0; i < q; ++i) {
		int s, t;
		scanf("%d %d", &s, &t);
		if (color[s] == color[t])
			cout << "yes" << endl;
		else
			cout << "no" << endl;
	}

	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)
#define len(x) ((int)(x).size())
#define mp make_pair
#define eb emplace_back
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;
constexpr int MAX = 1e6;
constexpr int NIL = -1;
int n;
vector<vi> G(MAX);
vi color(MAX, NIL), S;
inline void dfs(int r, int c) {
	S.eb(r);
	color[r] = c;
	int u, v;
	while(!S.empty()) {
		u = S.back(); S.pop_back();
		rep(i, 0, len(G[u])) {
			v = G[u][i];
			if(color[v] == NIL) {
				color[v] = c;
				S.eb(v);
			}
		}
	}
}
inline void assignColor() {
	int id = 0;
	rep(u, 0, n) {
		if(color[u] == NIL) dfs(u, ++id);
	}
}
int main() {
	int m;
	cin >> n >> m;
	int s, t;
	rep(i, 0, m) {
		cin >> s >> t;
		if(s > t) swap(s, t);
		G[s].eb(t);
	}
	assignColor();
	int q; cin >> q;
	rep(i, 0, q) {
		cin >> s >> t;
		P(color[s] == color[t] ? "yes" : "no");
	}
	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define rep(i,N) for(ll i=0;i<N;++i)
typedef long long int ll;
ll INF = 1LL<<60;

vector<vector<int> > G(100010);
vector<int> color(100010,-1);
int n,m; 

// sからたどり着く頂点の色をcに塗り替える
void dfs(int v, int c){
    stack<int> s;
    s.push(v);
    color[v] = c;
    while(!s.empty()){
        int u = s.top(); s.pop();
        for(auto nv : G[u]){
            if(color[nv] == -1){
                color[nv] = c;
                s.push(nv);
            }
        }
    }
}

void assignColor(){
    int number = 1;
    rep(i,n){
        if(color[i] == -1) dfs(i, number++);
    }
}

int main(){
        cin >> n >> m;
    rep(i,m){
        int x,y; cin >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
    }

    assignColor();
    int q; cin >> q;
    rep(i,q){
        int x,y; cin >> x >> y;
        if(color[x] == color[y]) cout << "yes" << endl;
        else cout << "no" << endl;
    }
}

C++: #include <iostream>
#include <vector>

using namespace std;

bool dfs(int s, int t, vector<vector<int>> sns, bool* visit) {
  if (s == t) {
    return true;
  }
  if (visit[s]) {
    return false;
  }

  visit[s] = true;

  int len = sns[s].size();
  for (int i = 0; i < len; i++) {
    int next = sns[s][i];
    if (dfs(next, t, sns, visit)) {
      return true;
    }
  }
  return false;
}

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

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

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

  cin >> q;
  for (int i = 0; i < q; i++) {
    cin >> s >> t;
    bool* visit = new bool[n];
    if (dfs(s, t, sns, visit)) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }
  return 0;
}

C++: #include <bits/stdc++.h>
#define be(v) (v).begin(),(v).end()
#define pb(q) push_back(q)
typedef long long ll;
using namespace std;
const ll mod=1000000007;
#define doublecout(a) cout<<fixed<<setprecision(10)<<a<<endl;
ll uni[100005];
ll root(ll u){
    if(uni[u]<0)return u;
    return uni[u]=root(uni[u]);
}

void connect(int a,int b){
    a=root(a);
    b=root(b);
    if(a==b)return;
    if(uni[a]<uni[b]){
        a^=b;
        b^=a;
        a^=b;
    }
    uni[a]+=uni[b];
    uni[b]=a;
    return;
}
ll size(ll u){
    return -uni[root(u)];
}
int main() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(false);
    memset(uni,-1,sizeof(uni));
    int n,m,q,a,b;
    cin>>n>>m;
    for(int i=0;i<m;i++){
    	cin>>a>>b;
    	connect(a,b);
    }
    vector<string> v;
    cin>>q;
    for(int i=0;i<q;i++){
    	cin>>a>>b;
    	if(root(a)==root(b))v.pb("yes");
    	else v.pb("no");
    }
    for(int i=0;i<q;i++){
    	cout << v[i] <<endl;
    }
    return 0;
}