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 <bits/stdc++.h>
using namespace std;

const int MAX=100005;
vector<int> S[MAX];

int par[MAX];
int root(int a){
    if(par[a]==a) return a;
    else return par[a]=root(par[a]);
}
void unite(int a,int b){
    if(root(a)!=root(b)) par[root(b)]=root(a);
}
bool check(int a,int b){
    return root(a)==root(b);
}

int main(){

    int N,M;cin>>N>>M;
    for(int i=0;i<N;i++){
        par[i]=i;
    }
    for(int i=0;i<M;i++){
        int a,b;cin>>a>>b;
        unite(a,b);
    }
    int Q;cin>>Q;
    for(int i=0;i<Q;i++){
        int a,b;cin>>a>>b;
        if(check(a,b)) cout<<"yes"<<endl;
        else cout<<"no"<<endl;
    }

}

C++: #include <bits/stdc++.h>
#define ll long long
#define INF 999999999
#define MOD 1000000007

using namespace std;

typedef pair<int,int>P;

const int MAX_N = 100000;

int par[MAX_N];
int rank[MAX_N];

void initial(int n){		//?????????
	for(int i=0;i<n;i++){
		par[i] = i;
		rank[i] = 0;
	}
}

int find(int x){		//??¨??????????±???????
	if(par[x] == x){
		return x;
	}else{
		return par[x] = find(par[x]);
	}
}

void unite(int x,int y){
	x = find(x);
	y = find(y);
	if(x == y) return;
	if(rank[x] < rank[y]){
		par[x] = y;
	}else{
		par[y] = x;
		if(rank[x] == rank[y])
			rank[x]++;
	}
}

bool same(int x,int y){
	return find(x) == find(y);
}

int main()
{
	int n,m,q;
	int a,b;
	cin >> n;
	cin >> m;
	initial(n);
	for(int i=0;i<m;i++){
		cin >> a;
		cin >> b;
		unite(a,b);
	}
	cin >> q;
	for(int i=0;i<q;i++){
		cin >> a;
		cin >> b;
		if(same(a,b)){
			cout << "yes\n";
		}else{
			cout << "no\n";
		}
	}
}

C++: #include <cstdio>
#include <queue>
#include <vector>

std::queue<int> q;
typedef struct{
	bool isVisited;
	std::vector<int> neighbors;
} node;

void bfs(node* nodes, int t){
	int id;
	while (!q.empty()){
		id = q.front();
		q.pop();
		if (!nodes[t].isVisited){
			for (int i=0; i<nodes[id].neighbors.size(); i++){
				if (!nodes[nodes[id].neighbors[i]].isVisited){
					q.push(nodes[id].neighbors[i]);
					nodes[nodes[id].neighbors[i]].isVisited=true;
				}
			}
		}
	}
	if (nodes[t].isVisited) printf("yes\n");
	else printf("no\n");
}

int main(){
	int n, d, num_relation, n_query, s, t;
	node *nodes;

	scanf("%d %d", &n, &num_relation);
	nodes = new node[n];
	for(int i=0;i<num_relation;i++){
		scanf("%d %d", &s, &t);
		nodes[s].neighbors.push_back(t);
		nodes[t].neighbors.push_back(s);
	}

	scanf("%d", &n_query);
	for(int i=0;i<n_query;i++){
		for (int j=0; j<n;j++){
			nodes[j].isVisited=false;
		}
		scanf("%d %d", &s, &t);
		q.push(s);
		bfs(nodes, t);
	}

	delete []nodes;
	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;
}

C++: #include <iostream>#include <vector>#include <queue>static const int MAX=100000;using namespace std;vector<int> follow[MAX];int color[MAX];  //-1 represent No Visitedvoid bfs(int i,int c){    queue<int> Q;    Q.push(i);color[i]=c;    while(!Q.empty())    {        int p=Q.front();Q.pop();        for(int j=0;j<follow[p].size();j++)        {            if(color[follow[p][j]]!=-1) continue;            //else            Q.push(follow[p][j]); color[follow[p][j]]=color[p];        }    }}int main(){   int n,m;   cin>>n>>m;   for(int i=0;i<n;i++) color[i]=-1;   for(int i=0;i<m;i++)   {       int a,b;       cin>>a>>b;       follow[a].push_back(b);       follow[b].push_back(a);   }   int c=0;   for(int i=0;i<n;i++)   {       if(color[i]==-1)       {           bfs(i, c);           c++;       }   }   int order_num;cin>>order_num;   for(int i=0;i< order_num;i++)   {       int a,b;       cin>>a>>b;       if(color[a]==color[b]) cout<<"yes"<<endl;       else cout<<"no"<<endl;   }}

C++: #include <stdio.h>
#include <iostream>
#include <utility>
#include <algorithm>
#include <math.h>
#include <vector>
#include <list>
#define N 100000
using namespace std;
int n;
list<int> adj[N];
bool f[N] = {};

bool PathExists(int u, int v)
{
    f[u] = true;
    if (u == v)
        return true;
    while (!adj[u].empty())
    {
        if (!f[adj[u].front()] && PathExists(adj[u].front(), v))
            return true;
        adj[u].pop_front();
    }

    return false;
}

int main()
{
    int m, u, v, q;
    cin >> n >> m;

    for (int i = 0; i < m; i++)
    {
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    cin >> q;
    for (int i = 0; i < q; i++)
    {
        cin >> u >> v;
        if (PathExists(u, v))
            printf("yes\n");
        else
            printf("no\n");
    }

    return 0;
}