Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	m := getNextInt(scanner)
	nodes := make([]Node, n)

	for i := 0; i < n; i++ {
		nodes[i].list = make([]int, 0)
	}

	for i := 0; i < m; i++ {
		s := getNextInt(scanner)
		t := getNextInt(scanner)
		nodes[s].list = append(nodes[s].list, t)
		nodes[t].list = append(nodes[t].list, s)
	}

	c := 1
	for i := 0; i < n; i++ {
		if nodes[i].c == 0 {
			traverse(nodes, i, c)
			c++
		}
	}

	q := getNextInt(scanner)

	for i := 0; i < q; i++ {
		s := getNextInt(scanner)
		t := getNextInt(scanner)
		if nodes[s].c == nodes[t].c {
			fmt.Fprintln(writer, "yes")
			continue
		}
		fmt.Fprintln(writer, "no")
	}

	writer.Flush()
}

// Node ...
type Node struct {
	list []int
	c    int
}

func traverse(nodes []Node, r, c int) {
	nodes[r].c = c
	for _, i := range nodes[r].list {
		if nodes[i].c != 0 {
			continue
		}
		traverse(nodes, i, c)
	}
}

C++: #include<iostream>
#include<queue>
#include<vector>
#include<cstring>
using namespace std;
queue<int>Q; int x[200000], n, m, q, s, t; vector<int>a[100000];

bool bfs(int A,int B) {
	memset(x, 0, sizeof(x));
	x[A] = 1;
	Q.push(A);
	while (!Q.empty() || x[B] == 0) {
		for (int k = 0; k < a[Q.front()].size(); k++) {
			if (x[a[Q.front()][k]] == 0) { 
				Q.push(a[Q.front()][k]); x[a[Q.front()][k]] = 1; 
				a[Q.front()].push_back(a[Q.front()][k]);
			}
		}
		Q.pop();
	}
	if (x[B] == 1) {
		while (!Q.empty()) { Q.pop(); }
		return true;
	}
	else {
		return false;
	}
}

int main() {
	cin >> n >> m;
	for (int i = 0; i < m; i++) {
		cin >> s >> t;
		a[s].push_back(t);
		a[t].push_back(s);
	}
	cin >> q;
	for (int i = 0; i < q; i++) {
		cin >> s >> t;
		if (bfs(s, t)) { cout << "yes" << endl; }
		else { cout << "no" << endl; }
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<stack>
#include<queue>
#include<algorithm>
#include<ctime>

void dfs(std::vector<std::vector<int> > &n) {
	/*
	std::stack<int> s;
	std::vector<std::vector<int> > nn(n.size());
	std::vector<int> dd(n.size());
	int count = 0;

	for (size_t i = 0; i < n.size(); i++) {
		if (dd[i] == 1)continue;
		nn[count].push_back(i);
		std::vector<int> d;
		s.push(i);
		while (s.size() != 0) {
			int num = s.top(); s.pop();
			d.push_back(num);
			dd[num] = 1;
			for (std::vector<int>::iterator it = n[num].begin(); it != n[num].end(); it++) {
				if (std::find(d.begin(), d.end(), *it) == d.end()) {
					nn[count].push_back(*it);
					s.push(*it);
					d.push_back(*it);
				}
			}
		}
		count++;
	}
	*/
	int question;
	std::cin >> question;

	for (int i = 0; i < question; i++) {
		int from, to;
		std::cin >> from >> to;
		std::stack<int> s;
		std::vector<int> went;
		s.push(from);
		bool flag = false;
		while (s.size() != 0 && flag == false){
			int num = s.top(); s.pop();
			for (size_t j = 0; j < n[num].size(); j++) {
				if (n[num][j] == to) {
					flag = true;
					break;
				}
				if (std::find(went.begin(), went.end(), n[num][j]) == went.end()) {
					s.push(n[num][j]);
					went.push_back(n[num][j]);
				}
			}
		}
		if (flag) {
			std::cout << "yes" << std::endl;
		} else {
			std::cout << "no" << std::endl;
		}
	}
	/*
	for (int i = 0; i < question; i++) {
		int from, to;
		std::cin >> from >> to;
		for (int j = 0; j < count; j++) {
			if (std::find(nn[j].begin(), nn[j].end(), from) != nn[j].end() &&
				std::find(nn[j].begin(), nn[j].end(), to) != nn[j].end()) {
				std::cout << "yes" << std::endl;
				break;
			}
			if (j == count - 1) {
				std::cout << "no" << std::endl;
			}
		}
	}
	*/
}

int main() {
	int people, relation;

	std::cin >> people >> relation;

	std::vector<std::vector<int> > n(people);

	for (int i = 0; i < relation; i++) {
		int from, to;
		std::cin >> from >> to;
		n[from].push_back(to);
		n[to].push_back(from);
	}

	dfs(n);

	return 0;
}

C++: /* 
 * ALDS1_11B.cpp
 */
#include <iostream>
#include <queue>
#include <cstdio>
#include <cstdlib>
#include <cstring>

using namespace std;

using Friends = vector<int>;
using SNS = vector<Friends>;

int n, m, q;
bool visited[100000];
SNS sns;

bool is_friend(int id, int target) {
    if (visited[id])
        return false;

    visited[id] = true;
    for (int i = 0; i < sns[id].size(); ++i) {
        int now = sns[id][i];
        if (now == target)
            return true;
    }

    for (int i = 0; i < sns[id].size(); ++i) {
        int now = sns[id][i];
        if (is_friend(now, target))
            return true;
    }
    return false;
}

int main(void) {

    scanf("%d %d", &n, &m);
    sns.resize(n);
    for (int i = 0, id, f; i < m; ++i) {
        scanf("%d %d", &id, &f);
        sns[id].push_back(f);
        sns[f].push_back(id);
    }

    scanf("%d", &q);
    for (int i = 0, id, f; i < q; ++i) {
        scanf("%d %d", &id, &f);
        memset(visited, 0, sizeof(bool) * n);
        if (is_friend(id, f))
            printf("yes\n");
        else
            printf("no\n");
    }

    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, 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;
}