Go: package main

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

func main() {
	var n,m int
	fmt.Scan(&n)
	group := make([]int, n)
	g := make([][]int, n)
	for i := 0; i < n; i++ {
		g[i] = []int{}
		group[i] = -1
	}
	
	fmt.Scan(&m)
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	for i := 0; i < m; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		
		g[s] = append(g[s], t)
		g[t] = append(g[t], s)
	}
	for i := 0; i < n; i++ {
		if group[i] != -1 {
			continue
		}
		q := []int{i}
		for len(q) > 0 {
			pop := q[0]
			if len(q) > 1 {
				q = q[1:]
			} else {
				q = []int{}
			}
			if group[pop] == -1 {
				q = append(q, g[pop]...)
				group[pop] = i
			}
		}
	}
	sc.Scan()
	q, _ := strconv.Atoi(sc.Text())
	for i := 0; i < q; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())

		if group[s] == group[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func root(i int, group *[]int) int {
	if i == (*group)[i] {
		return i
	}
	(*group)[i] = root((*group)[i], group)
	return (*group)[i]
}

C++: #include <bits/stdc++.h>
using namespace std;
int n, m;
vector< vector<int> > v;
vector<bool> used;

bool dfs(int pos, int dest){
  if(used[pos]) return false;
  used[pos] = true;
  if(pos == dest) return true;
  for(int i = 0; i < v[pos].size(); i++){
    if(dfs(v[pos][i], dest)){
      return true;
    }
  }
  return false;
}

int main(void){
  ios::sync_with_stdio(false);
  cin.tie(0);

  cin >> n >> m;
  v = vector< vector<int> >(n, vector<int>(0));
  used = vector<bool>(n, false);
  for(int i = 0; i < m; i++){
    int a, b; cin >> a >> b;
    v[a].push_back(b);
    v[b].push_back(a);
  }
  int q; cin >> q;
  for(int i = 0; i < q; i++){
    used = vector<bool>(n, false);
    int a, b; cin >> a >> b;
    if(dfs(a, b)){
      cout << "yes" << endl;
    }else{
      cout << "no" << endl;
    }
  }
  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;
        }
    }
    
    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;
        if(ds.same(s, t)) cout << "yes" << endl;
        else cout << "no" << endl;
    }
    return 0;
}