Go: package main

import (
	"bufio"
	"container/list"
	"fmt"
	"os"
	"strconv"
)

//util
var sc = bufio.NewScanner(os.Stdin)

func nextStr() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	n := len(list)
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list[0 : n-1] {
		buf.Write([]byte(fmt.Sprintf("%d ", v)))
	}
	buf.Write([]byte(fmt.Sprintf("%d\n", list[n-1])))
	buf.Flush()
}

func max(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func min(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

//solve
const (
	MAX = 100000
	NIL = -1
)

var (
	n, m, q, s, t int
	G             [MAX][]int //連結リスト
	color         [MAX]int
)

func dfs(r int, c int) {
	S := list.New()
	S.PushFront(r)
	color[r] = c
	for S.Len() != 0 {
		u := S.Remove(S.Front()).(int)
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == NIL {
				color[v] = c
				S.PushFront(v)
			}
		}
	}
}

//幅優先探索で、頂点を色付け
func assignColor() {
	id := 1
	for i := 0; i < n; i++ {
		color[i] = NIL
	}
	for i := 0; i < n; i++ {
		if color[i] == NIL {
			id++
			dfs(i, id)
		}
	}
}

func main() {
	sc.Split(bufio.ScanWords)
	n, m = nextInt(), nextInt()
	for i := 0; i < m; i++ {
		s, t = nextInt(), nextInt()
		if i == 0 {
			G[s] = make([]int, 0)
			G[t] = make([]int, 0)
		}
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)

	}
	assignColor()
	q = nextInt()
	for i := 0; i < q; i++ {
		s, t = nextInt(), nextInt()
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}

}

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

vector<vector<int> > G;
vector<int> is_visited;
int b;

bool DFS(int a, int i) {
    if (a == b) return true;
    if (i >= G[a].size()) return false;
    is_visited[a] = 1;
    if (!is_visited[G[a][i]] && DFS(G[a][i], 0)) {
        return true;
    }
    return DFS(a, i + 1);
}

// bool DFS(const vector<vector<int> >& G,
//          vector<bool>& is_visited, int a, int b, int i) {
//     if (a == b) return true;
//     if (i >= G[a].size()) return false;
//     is_visited[a] = true;
//     if (!is_visited[G[a][i]] && DFS(G, is_visited, G[a][i], b, 0)) {
//         return true;
//     }
//     return DFS(G, is_visited, a, b, i + 1);
// }

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

    G.resize(n);
    is_visited.resize(n);

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

// for (int i = 0; i < n; i++) {
//     cout << i << " : ";
//     for (int j = 0; j < G[i].size(); j++){
//         cout << G[i][j] << " ";
//     }
//     cout << endl;
// }



    int q;
    cin >> q;
    for (int i = 0; i < q; i++) {
        int a;
        cin >> a >> b;
        for (int j = 0; j < n; j++) {
            is_visited[j] = 0;
        }
        if (DFS(a, 0)) {
            cout << "yes" << endl;
        } else {
            cout << "no"  << endl;
        }
    }
    return 0;
}

C++: #include<iostream>
using namespace std;
#define MAX 101000

int ran[MAX], par[MAX];

int init(int n){
	for(int i = 0; i < n; i++){
		ran[i] = 0;
		par[i] = i;
	}
}

int find(int x){
	return par[x] ==  x ? x : par[x] = find(par[x]);
}

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

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


int main(){
	int n, m, q, s, t;
	
	cin>>n>>m;
	
	init(n);
	
	for(int i = 0; i < m; i++){
		cin>>s>>t;
		unite(s,t);
	}
	
	cin>>q;
	
	for(int i = 0; i < q; i++){
		cin>>s>>t;
		cout<<(same(s,t)?"yes":"no")<<endl;
	}
	
	
	return 0;
}