Go: package main

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

const MAX = 100000

type Queue struct {
	head      int
	tail      int
	container [MAX]int
}

func (q *Queue) push(n int) {
	q.container[q.tail] = n
	q.tail = (q.tail + 1) % MAX
}

func (q *Queue) pop() int {
	res := q.container[q.head]
	q.head = (q.head + 1) % MAX
	return res
}

func (q *Queue) isEmpty() bool {
	return q.head == q.tail
}

var sc = bufio.NewScanner(os.Stdin)
var route [][]int
var SEEN [MAX]bool
var GROUP [MAX]int

func scanInt() int {
	num, _ := strconv.Atoi(scanString())
	return num
}

func scanString() string {
	sc.Scan()
	return sc.Text()
}

func init() {
	sc.Split(bufio.ScanWords)
}

func bfs(start, group int) {
	que := Queue{}
	que.push(start)

	for !que.isEmpty() {
		id := que.pop()

		if SEEN[id] {
			continue
		}
		SEEN[id] = true
		GROUP[id] = group

		for _, next := range route[id] {
			que.push(next)
		}
	}
}

func main() {
	n, m := scanInt(), scanInt()
	route = make([][]int, n)
	for i := 0; i < m; i++ {
		s, t := scanInt(), scanInt()
		route[s] = append(route[s], t)
		route[t] = append(route[t], s)
	}

	for i := 0; i < n; i++ {
		if !SEEN[i] {
			bfs(i, i+1)
		}
	}

	w := bufio.NewWriter(os.Stdout)
	q := scanInt()
	for i := 0; i < q; i++ {
		s, t := scanInt(), scanInt()
		if GROUP[s] == GROUP[t] {
			fmt.Fprintln(w, "yes")
		} else {
			fmt.Fprintln(w, "no")
		}
	}
	w.Flush()
}

C++: #include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
const ll mod = ll(1e9) + 7;
const int INF = int(1e9);

int par[100000]; //parent
int rnk[100000]; //depth

//init with n elements
void init(int n) {
	for (int i = 0; i < n; i++) {
		par[i] = i;
		rnk[i] = 0;
	}
}
//find a root of the tree
int find(int x) {
	if (par[x] == x) {
		return x;
	}
	else {
		return par[x] = find(par[x]);
	}
}

//merge the sets contains x,y
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]++;
	}
}

//the set contains x and y or not
bool same(int x, int y) {
	return find(x) == find(y);
}
int main()
{
    int n,m;
    cin>>n>>m;
    init(n);
    rep(i,m){
        int a,b;
        cin>>a>>b;
        unite(a,b);
    }
    int q;
    cin>>q;
    vector<string>ans(q);
    rep(i,q){
        int a,b;
        cin>>a>>b;
        if(same(a,b))ans[i]="yes";
        else ans[i]="no";
    }
    rep(i,q)cout<<ans[i]<<endl;
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <queue>
using namespace std;
int main(){
        int N,M;
        cin >> N >> M;
        vector <vector <int> > friends(N,vector <int>(N));
        vector <int> groups(N,-1);
        for(int i=0 ; i<M ; i++ ){
                int s,t;
                cin >> s >> t;
                friends[s][t]=friends[t][s]=1;
        }
        int group=0;
        for(int i=0 ; i<N ; i++ ){
                if(groups[i]!=-1)
                        continue;
                queue <int> cycle;
                cycle.push(i);
                while(cycle.size()!=0){
                        int now=cycle.front();cycle.pop();
                        for(int l=0 ; l<N ; l++ ){
                                if(friends[now][l] && groups[l]==-1 )
                                        cycle.push(l);
                        }
                        groups[now]=group;
                }
                group++;
        }
        cin >> N;
        for(int i=0 ; i<N ; i++ ){
                int s,t;
                cin >> s>> t;
                if(groups[s]==groups[t])
                        cout<<"yes"<<endl;
                else
                        cout<<"no"<<endl;
        }
        return 0;
}

C++: #include <iostream>

using namespace std;

const int N = 100000;
int A[N][N] = {{0}};
int n;

bool dfs(int s, int t) {
    if (A[s][t] == 1) {
        return true;
    }
    for (int i = 0; i < n; ++i) {
        if (i != t && A[s][i] != 0) {
            if (dfs(i, t)) {
                return true;
            }
        }
    }
    return false;
}

int main() {
    int m;
    cin >> n >> m;
    for (int i = 0; i < m; ++i) {
        int s, t;
        cin >> s >> t;
        A[s][t] = 1;
    }

    int q;
    cin >> q;
    for (int j = 0; j < q; ++j) {
        int x, y;
        cin >> x >> y;

        if (dfs(x, y)) {
            cout << "yes";
        } else {
            cout << "no";
        }
        cout << endl;
    }

    return 0;
}