Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var (
	n     int
	G     [100000][]int
	color [100000]*int
)

func dfs(r int, c int) {
	S := Stack{}
	S.Push(r)
	color[r] = &c
	for !S.IsEmpty() {
		u := S.Pop()
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == nil {
				color[v] = &c
				S.Push(v)
			}
		}
	}
}

func assignColor() {
	id := 1
	for i := 0; i < n; i++ {
		color[i] = nil
	}
	for u := 0; u < n; u++ {
		if color[u] == nil {
			id++
			dfs(u, id)
		}
	}
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan()
	n, _ = strconv.Atoi(sc.Text())
	sc.Scan()
	r, _ := strconv.Atoi(sc.Text())

	for i := 0; i < r; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	assignColor()
	sc.Scan()
	qNum, _ := strconv.Atoi(sc.Text())
	for i := 0; i < qNum; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

// Stack is Stack
type Stack struct {
	stack []int
}

// Push new value
func (stack *Stack) Push(val int) {
	stack.stack = append(stack.stack, val)
}

// Pop new value
func (stack *Stack) Pop() int {
	val := stack.stack[len(stack.stack)-1]
	stack.stack = stack.stack[0 : len(stack.stack)-1]
	return val
}

// IsEmpty return true when stack is empty
func (stack *Stack) IsEmpty() bool {
	return len(stack.stack) == 0
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <list>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <sstream>
#include <cmath>
#include <functional>
#include <fstream>
#include <cstdlib>
typedef long long ll;
const int MOD = 1e9+7;


#define REP(i, N) for (int i = 0; i < (N); i++)
#define REPP(i, a, b) for (int i = (a); i < (b); i++)
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define VSORT(c) sort((c).begin(),(c).end())
#define SZ(x) ((int)(x).size())
//vvintを作る　マクロで　 #define vvint(N,M) vector<vector<int>>

using namespace std;
vector<int> group_id(100001);
vector<vector<int> > groups(100001);
int n;
void dfs(int i ,int c){
    stack<int> s;
    s.push(i);
    group_id[i] = c;
    while(!s.empty()){
        int u = s.top();s.pop();
        for(int l = 0; l < groups[u].size();l++){
            int g = groups[u][l];
            if(group_id[g] == -1){
                group_id[g] = c;
                s.push(g);
            }
        }
    }
}
void makeGroup(){
    int id = 0;
    for(int i = 0; i < n;i++) group_id[i] = -1;
    for(int i = 0; i < n;i++){
        if(group_id[i] == -1){
            dfs(i,id++);
        }
    }
}


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

    cin >> n >> m;

    int f,s;
    for(int i = 0; i < m;i++){
        cin >> f >> s;
        groups[f].push_back(s);
        groups[s].push_back(f);
    }

    makeGroup();

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

    // for(int i = 0; i < n;i++){
    //     cout << i << " : " << group_id[i] << endl;
    // }


    return 0;
}

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" << "\n";
    }else{
      cout << "no" << "\n";
    }
  }

  return 0;
}

C++: #include <iostream>
#include <list>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <algorithm>
#include <cmath>
#include <string>
using namespace std;
typedef long long lli;
typedef vector<lli> vll;
typedef vector<bool> vbl;
typedef vector<vector<lli> > mat;
typedef vector<vector<bool> > matb;
typedef vector<string> vst;
typedef pair<lli,lli> pll;
typedef pair<double,double> pdd;

vll par;
vll rnk;
void init(lli n){
    par = vll(n);
    rnk = vll(n);
    for(lli i = 0;i < n;i++) par[i] = i;
}
lli find(lli x){
    if(par[x] == x) return x;
    else return par[x] = find(par[x]);
}
void unite(lli x,lli 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(lli x,lli y){
    return find(x) == find(y);
}

lli n,m,q;
lli s,t;

int main(){
    cin >> n >> m;
    init(n);
    for(lli i = 0;i < m;i++){
        cin >> s >> t;
        unite(s,t);
    }
    cin >> q;
    for(lli i = 0;i < q;i++){
        cin >> s >> t;
        cout << (same(s,t) ? "yes" : "no" ) << endl;
    }
    return 0;
}

C++: #include<stack>
#include<queue>
#include<conio.h>
#include<string>
#include<vector>
#include<iostream>
#include<algorithm>
using namespace std;
queue<int> Q;
vector<int> G[100000];
bool flag = false;
int s, t;
int color[100000];

void a(){
	while (!Q.empty()){
		Q.pop();
		for (int i = 0; i < G[s].size(); i++){
			//_getch();
			//cout << G[s][i] << endl;
			if (G[s][i] == t){
				flag = true;
				while (!Q.empty()) Q.pop();
				return;
			}
			else if (color[i] == 0){
				Q.push(G[s][i]);
				color[i] = 1;
			}
		}
		if (!Q.empty())s = Q.front();
	}
}

int main(){
	int n, 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);
	}
	cin >> q; fill(color, color + 100000, 0);
	for (int i = 0; i < q; i++){
		cin >> s >> t;
		Q.push(s);
		a();
		if (flag) cout << "yes" << endl;
		else cout << "no" << endl;
		flag = false;
		fill(color, color + 100000, 0);
	}

	return 0;
}

C++: #define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
using namespace std;
#define MAX (int)1e5

vector<int> G[MAX];
queue<int> qu;

int main() {
	int n, m, q;
	int ind,tmp;
	cin >> n >> m;
	bool flag = 0;
	for (int i = 0; i < m; i++) {
		cin >> ind >> tmp;
		G[ind].push_back(tmp);
		G[tmp].push_back(ind);
	}
	cin >> q;
	for (int i = 0; i < q; i++) {
		cin >> ind >> tmp;
		flag = 0;
		qu.push(ind);
		while (not qu.empty()) {
			int u = qu.front(); qu.pop();
			if (u == tmp) {
				flag = 1;
				break;
			}
			for (int j = 0; j < G[u].size(); j++) {
				qu.push(G[u][j]);
			}
		}
		if (flag) cout << "yes" << endl;
		else cout << "no" << endl;
	}
}

C++: #include <vector>
#include <iostream>
using namespace std;
int n, m, q, x, y; int group[100000]; vector<int> f[100000];
int main() {
	scanf("%d%d", &n, &m);
	for(int i = 0; i < n; i++) group[i] = i, f[i].push_back(i);
	for(int i = 0; i < m; i++) {
		scanf("%d%d", &x, &y);
		if(group[x] == group[y]) continue;
		x = group[x], y = group[y];
		if(f[y].size() > f[x].size()) swap(x, y);
		for(int j = f[y].size() - 1; j >= 0; j--) {
			group[f[y][j]] = group[x];
			f[x].push_back(f[y][j]);
			f[y].pop_back();
		}
	}
	scanf("%d", &q);
	for(int i = 0; i < q; i++) {
		scanf("%d%d", &x, &y);
		printf("%s\n", group[x] == group[y] ? "yes" : "no");
	}
	return 0;
}