Go: package main

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

// Node 頂点
type Node struct {
	gid  int   // グループID
	edge []int // 隣接辺
}

// NoID グループIDなし
const NoID = -1

// NewNode 頂点の生成
func NewNode() *Node {
	return &Node{gid: NoID, edge: []int{}}
}

func parseNode(nodes []*Node, gid int, queue []int) {
	if len(queue) == 0 {
		return
	}
	var nextQ []int
	for _, id := range queue {
		node := nodes[id]
		if node.gid == NoID {
			node.gid = gid
			for _, edge := range node.edge {
				nextQ = append(nextQ, edge)
			}
		}
	}
	parseNode(nodes, gid, nextQ)
	return
}
func digNode(nodes []*Node, id, gid int) {
	node := nodes[id]
	if node.gid != NoID {
		// 探索済み
		return
	}
	node.gid = gid
	for _, edge := range node.edge {
		digNode(nodes, edge, gid)
	}
	return
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	n, m := eGetInt2(scanner)

	nodes := make([]*Node, n)
	for i := 0; i < n; i++ {
		nodes[i] = NewNode()
	}

	for i := 0; i < m; i++ {
		a, b := eGetInt2(scanner)
		nodes[a].edge = append(nodes[a].edge, b)
		nodes[b].edge = append(nodes[b].edge, a)
	}

	for i := 0; i < n; i++ {
		// 幅優先探索
		// gid := i
		// queue := []int{i}
		// parseNode(nodes, gid, queue)

		// 深さ優先探索
		digNode(nodes, i, i)
	}

	q := eGetInt(scanner)
	for i := 0; i < q; i++ {
		a, b := eGetInt2(scanner)
		if nodes[a].gid == nodes[b].gid {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func eGetInt(scanner *bufio.Scanner) int {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0]
}
func eGetInt2(scanner *bufio.Scanner) (int, int) {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0], t[1]
}

func eGetline(p *bufio.Scanner) string {
	if !p.Scan() {
		if err := p.Err(); err != nil {
			log.Fatal(err.Error())
		}
		return ""
	}
	return p.Text()
}

func eAtoi(s []string) []int {
	ints := make([]int, len(s))
	var err error
	for i, e := range s {
		ints[i], err = strconv.Atoi(e)
		if err != nil {
			log.Fatal(err.Error())
		}
	}
	return ints
}

C++: #include <iostream>
#include <stack>
#include <vector>
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 v, int id)
{
    stack<int> S;
    S.push(v);
    color[v] = id;
    int u;
    while (!S.empty()) {
        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] = id;
                S.push(v);
            }
        }
    }
}

void assignColor()
{
    int id = 1;
    for (int i = 0; i < n; i++) {
        color[i] = NIL;
    }
    for (int i = 0; i < n; i++) {
        if (color[i] == NIL) {
            dfs(i, id++);
        }
    }
}

int main(int argc, char const *argv[])
{
    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" << endl;
        } else {
            cout << "no" << endl;
        }
    }
    return 0;
}

C++: #include<iostream>
#include<list>
#include<iterator>
#define MAX 100000
using namespace std;
char ans[MAX + 1];

class person
{
public:
	int id;
	bool Isdone = false;
	list <person*> lis;
	bool serch(person* Per)
	{
		if (ans[Per->id] == 1)return true;
		else if (ans[Per->id] == -1)return false;
		Isdone = true;
		for(list<person*>::iterator temp=lis.begin();temp!=lis.end();++temp)
		{
			if ((*temp) == Per)
			{
				ans[(*temp)->id] = 1;
				return true;
			}
			else if ((*temp)->Isdone == true)continue;
			else
			{
				if ((*temp)->serch(Per))
				{
					ans[(*temp)->id] = 1;
					return true;
				}
			}
		}
		ans[Per->id] = -1;
		return false;
	}
};

person P[MAX + 1];

int main()
{
	int n, m;
	cin >> n >> m;
	for (int i = 0; i < n; i++)P[i].id = i;
	for (int i = 0; i < m; i++)
	{
		int p1, p2;
		scanf("%d%d",&p1, &p2);
		P[p1].lis.push_back(&P[p2]);
		P[p2].lis.push_back(&P[p1]);
	}			 
	int q;
	cin >> q;
	for (int i = 0; i < q; i++)
	{
		int p1, p2;
		scanf("%d%d", &p1, &p2);
		if (P[p1].serch(&P[p2]))
		{
			cout << "yes" << endl;
		}
		else
		{
			cout << "no" << endl;
		}
		for (int l = 0; l < n; l++)P[l].Isdone = false;
		for (int l = 0; l < n; l++)ans[l] = 0;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n); i >= 0; i--)
#define REP(i, m, n) for (int i = (int)(m); i <= (int)(n); i++)
#define REPR(i, m, n) for (int i = (int)(m); i >= (int)(n); i--)
#define all(v) v.begin(), v.end()
typedef long long ll;

using Graph = vector<vector<int> >;

vector<int> seen;

void dfs(const Graph &G, int v, int c){
  seen[v] = c;

  for(int nv : G[v]){
    if(seen[nv] != -1) continue;
    dfs(G, nv, c);
  }
}

int main(){
  int n, m; cin >> n >> m;

  Graph G(n);
  rep(i, m){
    int a, b; cin >> a >> b;
    G[a].push_back(b);
    G[b].push_back(a);
  }

  seen.assign(n, -1);
  int c = 0;
  rep(i, n){
    if(seen[i] == -1){
      dfs(G, i, c);
      c++;
    }
  }

  int q; cin >> q;
  rep(i, q){
    int s, t; cin >> s >> t;
    cout << (seen[s] == seen[t] ? "yes" : "no") << endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

int main()
{
	int n, m;
	cin >> n >> m;
	vector<vector<int>> g( n );
	for( int i = 0; i < m; i++ ) {
		int s, t;
		cin >> s >> t;
		g[s].push_back( t );
		g[t].push_back( s );
	}
	vector<int> color( n );
	int col = 0;
	for( int i = 0; i < n; i++ ) {
		if( color[i] > 0 ) continue;
		col++;
		color[i] = col;
		queue<int> que;
		que.push( i );
		while( !que.empty() ) {
			int u = que.front();
			que.pop();
			for( auto v : g[u] ) {
				if( color[v] > 0 ) continue;
				que.push( v );
				color[v] = col;
			}
		}
	}

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

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

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