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<vector>
#include<stack>

using namespace std;

static const int MAX = 100000;
static const int NIL = -1;

int n;
vector<int> G[MAX]
int color[N];

void dfs(int r, int c) {
  stack<int> S;
  S.push(s);
  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 m, s, t;

  cin >> n >> m;

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

  assignColor();

  int q;
  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 <cstdio>
#include <queue>
#include <vector>

typedef struct{
	std::vector<int> neighbors;
	int cluster;
} node;

void dfs(node* nodes, int id, int cluster){
	for (int i=0; i<nodes[id].neighbors.size(); i++){
		if (nodes[nodes[id].neighbors[i]].cluster == -1){
			nodes[nodes[id].neighbors[i]].cluster = cluster;
			dfs(nodes, nodes[id].neighbors[i], cluster);
		}
	}
}

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

	scanf("%d %d", &n, &num_relation);
	nodes = new node[n];
	for (int i=0; i<n;i++){
		nodes[i].cluster = -1;
	}
	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);
	}
	cluster = -1;
	for (int i=0;i<n;i++){
		cluster ++;
		if (nodes[i].cluster == -1) dfs(nodes, i, cluster);
	}
	scanf("%d", &n_query);
	for(int i=0;i<n_query;i++){
		scanf("%d %d", &s, &t);
		if (nodes[s].cluster == nodes[t].cluster) printf("yes\n");
		else printf("no\n");

	}

	delete []nodes;
	return 0;
}

C++: #include <cstdio>
#include <algorithm>
#include <unordered_set>

int main(){
    int n;
    int m;
    std::scanf("%d", &n);
    std::scanf("%d", &m);
    static std::unordered_set<int> relations[100000];
    int rCount = 0;
    for(int i = 0; i < m; ++i){
        int s;
        int t;
        std::scanf("%d", &s);
        std::scanf("%d", &t);
        bool find = false;
        for(int j = 0; j < rCount; ++j){
            if(relations[j].find(s) != relations[j].end()){
                if(relations[j].find(t) == relations[j].end()){
                    relations[j].insert(t);
                }
                find = true;
                break;
            } else if(relations[j].find(t) != relations[j].end()){
                if(relations[j].find(s) == relations[j].end()){
                    relations[j].insert(s);
                }
                find = true;
                break;
            }
        }
        if(find == false){
            relations[rCount].insert(s);
            relations[rCount].insert(t);
            ++rCount;
        }
    }
    int q;
    std::scanf("%d", &q);
    for(int i = 0; i < q; ++i){
        int s;
        int t;
        std::scanf("%d", &s);
        std::scanf("%d", &t);
        bool find = false;
        for(int j = 0; j < rCount; ++j){
            if(relations[j].find(s) != relations[j].end() && relations[j].find(t) != relations[j].end()){
                find = true;
                break;
            }
        }
        if(find){
            std::printf("yes\n");
        } else {
            std::printf("no\n");
        }
    }

    return 0;
}

C++: #include <iostream>
#include <vector>
using namespace std;

const int MAX = 100000;
vector<int> G[MAX];

class DisjointSet{
public:
    vector<int> rank, parent;
    DisjointSet();
    DisjointSet(int size){
        rank.resize(size,0);
        parent.resize(size,0);
        for (int i=0; i<size; i++) {
            makeSet(i);
        }
    }

//    bool same(int u,int v){
//        if (parent[u] == parent[v]) {
//            return true;
//        }else{
//            return false;
//        }
//    }
    bool same(int u,int v){
        int x = findSet(u); int y= findSet(v);
        return x==y;
    }
    
    void unite(int u,int v){
        int x = findSet(u);int y= findSet(v);
        if(rank[x]<rank[y]){
            parent[x] = y;
        }else{
            parent[y] = x;
            if(rank[x]==rank[y]){
                rank[x]++;
            }
        }
    }
    // ????????????????????????
    int findSet(int u){
        
        if(u!=parent[u])
            parent[u] = findSet(parent[u]);
        
        return parent[u];
    }
private:
    void makeSet(int i){
        rank[i] = 0;
        parent[i] = i;
    }
};
    
int main(int argc, const char * argv[]) {
    
    int n,m;
    cin >> n >> m;
    DisjointSet ds(n);
    
    for(int i=0;i<m;i++){
        int s,t;
        cin >> s >> t;
        ds.unite(s, t);
    }
    int q;
    cin >> q;
    for(int i=0;i<q;i++){
        int s,t;
        cin >> s >> t;
        if(ds.same(s, t)) cout << "yes" << endl;
        else cout << "no" << endl;
    }
    return 0;
}