Go: package main

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

const (
	MAX = 100000
	NIL = -1
)

var (
	n     int
	G     [MAX][]int
	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)
			}
		}
	}
}

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() {
	var s, t, m, q int
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	scanner.Scan()
	n, _ = strconv.Atoi(scanner.Text())
	scanner.Scan()
	m, _ = strconv.Atoi(scanner.Text())
	for i := 0; i < m; i++ {
		scanner.Scan()
		s, _ = strconv.Atoi(scanner.Text())
		scanner.Scan()
		t, _ = strconv.Atoi(scanner.Text())
		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()
	scanner.Scan()
	q, _ = strconv.Atoi(scanner.Text())
	for i := 0; i < q; i++ {
		scanner.Scan()
		s, _ = strconv.Atoi(scanner.Text())
		scanner.Scan()
		t, _ = strconv.Atoi(scanner.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <string>
#define N 100

void input_graph(std::vector<std::vector<int> >& g, int m){
    int s, t;
    for(int i=0; i<m; i++){//双連結リストを作る
        std::cin >> s >> t;
        g[s].push_back(t);
        g[t].push_back(s);
    }
}

void result(std::string ans[], int q){
    for(int i=0; i<q; i++){
        std::cout << ans[i] << '\n';
    }
}

void CC(std::vector<std::vector<int> >& g, std::string ans[], int q, int n){
    int s, t;
    int cnt = 0;
    std::vector<int> tmp;   //軌跡を保存
    //深さ優先探索
    while(cnt < q){
        //std::cout << "OK" << cnt << '\n';
        std::cin >> s >> t;
        int i = s;
        int nexti;
        int j;
        bool flag[n] = {false};
        bool f = false; //false:未到達 true:到達or終了
        while(!f){
            while(i != -1){
                //std::cout << "start\n";
                tmp.push_back(i);
                //std::cout << "i:" << i << '\n';
                flag[i] = true;
                //次の葉を探す
                if((int)g[i].size() != 0){//葉が最深でないとき
                    j = 0;
                    nexti = g[i][j];
                    while(flag[nexti]){
                        j++;
                        if(j == (int)g[i].size()){//葉がすべて探索済みなら
                            i = -1; //2つ目のwhile文を抜ける
                            break;
                        }
                        nexti = g[i][j];
                    }
                    if(i != -1){
                        if(nexti == t){
                            ans[cnt] = "yes";
                            i = -1;
                            f = true;
                            break;
                        }
                        i = nexti;
                    }
                }
                else{//葉が最深のとき
                    i = -1;
                }
            }
            if(!f){//まだ到達していなければ
                //ここから根に向かって戻る. 未探索の葉があればそちらへ行く
                //std::cout << "back\n";
                tmp.pop_back();
                i = (int)tmp.back();
                //std::cout << "i:" << i << '\n';
                tmp.pop_back();
                j = 0;
                nexti = g[i][j];
                while(flag[nexti]){
                    j++;
                    if(j == (int)g[i].size()){//現在のノードから未探索の葉がない
                        if((int)tmp.size() != 0){//まだtmpに軌跡が残っているなら
                            i = (int)tmp.back();
                            //std::cout << "i:" << i << '\n';
                            tmp.pop_back();
                            j = 0;
                            nexti = g[i][j];
                        }
                        else{//tmpに軌跡が残っていないなら
                            ans[cnt] = "no";
                            f = true;
                            break;
                        }
                    }
                }
            }
            i = nexti;
        }
        tmp.clear();    //一応clear
        cnt++;          //次のquestionへ
    }
}

int main(){
    int n, m;
    std::cin >> n >> m;
    std::vector<std::vector<int> > g;
    g.resize(n);
    input_graph(g, m);
    int q;
    std::cin >> q;          //質問数
    std::string ans[q];     //yes or no
    CC(g, ans, q, n);
    result(ans, q);
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <unordered_set>
#include <unordered_map>
#include <algorithm>
//#include "../cxx-prettyprint/prettyprint.hpp"

std::vector<std::vector<int>> Adj;
std::unordered_set<int> nodes_unvisited;
std::unordered_map<int, int> node_component_map;

void mark_nodes(int node, int component_id) {
    node_component_map[node] = component_id;
    nodes_unvisited.erase(node);
    for (int& next : Adj[node]) {
        if (nodes_unvisited.find(next) != nodes_unvisited.end()) {
            mark_nodes(next, component_id);
        }
    }
}

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

    Adj.assign(n, std::vector<int>());
    for (int i = 0; i < m; i++) {
        int s, t;
        std::cin >> s >> t;
        Adj[s].push_back(t);
        Adj[t].push_back(s);
    }

    for (int i = 0; i < n; i ++) {
        nodes_unvisited.insert(i);
    }

    int component_id = 0;
    while (!nodes_unvisited.empty()) {
        int start = *nodes_unvisited.begin();
        mark_nodes(start, component_id);
        component_id ++;
    }

    int q;
    std::cin >> q;
    for (int i = 0; i < q; i ++) {
        int s, t;
        std::cin >> s >> t;
        if (node_component_map[s] == node_component_map[t]) {
            std::cout << "yes" << std::endl;
        } else {
            std::cout << "no" << std::endl;
        }
    }
}

C++: #include <cstdio>
#include <vector>
#include <queue>
using namespace std;
static const int NIL = -1;

int n, m;
int *color;
vector<int> *v;

void bfs(int r, int c) {
    queue<int> q;
    q.push(r);
    while (!q.empty()) {
        int u = q.front();
        q.pop();
        if (color[u] == NIL) {
            color[u] = c;
        }
        for (vector<int>::iterator it = v[u].begin(); it != v[u].end(); it++) {
            if (color[*it] == NIL) {
                q.push(*it);
            }
        }
    }
}

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

int main() {
    scanf("%d %d", &n, &m);
    v = new vector<int>[n];

    for (int i = 0; i < m; i++) {
        int s, t;
        scanf("%d %d", &s, &t);
        v[s].push_back(t);
        v[t].push_back(s);
    }

    assignColor();

    int q;
    scanf("%d", &q);

    for (int i = 0; i < q; i++) {
        int s, t;
        scanf("%d %d", &s, &t);
        printf("%s\n", color[s] == color[t] ? "yes" : "no");
    }

    return 0;
}

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

using namespace std;

int main() {
  vector<int> R[100000];
  queue<int> Q;
  int n,m,s,t,q;
  int visit[100000];

  cin >> n >> m;
  for(int i=0;i<m;i++){
    cin >> s >> t;
    R[s].push_back(t);
    R[t].push_back(s);
  }
  
  for(int j=0;j<n;j++) visit[j] = 0;
  for(int i=0;i<n;i++){
    if(visit[i] == 0){
      Q.push(i);
      while(Q.empty() == false){
	int u = Q.front();
	Q.pop();
	visit[u] = 1;
	for(int j=0;j<R[u].size();j++){
	  int v = R[u][j];
	  if(visit[v]==0)Q.push(v);
	}
	R[u].clear();
	R[u].push_back(i);
      }
    }
  }
    
  cin >> q;
  for(int i=0;i<q;i++){
    cin >> s >> t;
    if(R[s][0] == R[t][0]) cout << "yes" << endl;
    else cout << "no" << endl;
  }


  return 0;
}