Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

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

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N, M := sc.nextInt(), sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < M; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	group := make([]int, N)
	for i := 0; i < N; i++ {
		group[i] = -1
	}
	var dfs func(cur int)
	dfs = func(cur int) {
		for i := 0; i < len(G[cur]); i++ {
			next := G[cur][i]
			if group[next] == -1 {
				group[next] = group[cur]
				dfs(next)
			}
		}
	}
	num := 0
	for i := 0; i < N; i++ {
		if group[i] == -1 {
			group[i] = num
			dfs(i)
			num++
		}
	}

	Q := sc.nextInt()
	for i := 0; i < Q; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		if group[s] == group[t] {
			fmt.Fprintln(wtr, "yes")
		} else {
			fmt.Fprintln(wtr, "no")
		}
	}
	wtr.Flush()
}

C++: #include<cstdio>
#include<vector>
#define N 100000
using namespace std;

vector<int> G[N];
/*
??£??\??????????????????????????°???????????¨??????????????£????????????????????????DFS??§????????????

 */
int labels[N], c=0;

void dfs_init(){
    int i;
    for(i=0;i<N; i++)labels[i]=0;
}

/*
  ?????°?????¨??????????£?
  ??§???????????????????????????
  stack???????????°??§???????????????
 */
bool dfs(int u, int v){
    if (u == v) return true;
    labels[u] = 1;
    int i,x;
    for(i=0; i<G[u].size(); i++){
	x = G[u][i];
	dfs(x,v);
    }
    return false;
}

void dfs2(int u){
    labels[u]=c;
    int i;
    for(i=0; i<G[u].size(); i++){
	if (labels[G[u][i]]==0) dfs2(G[u][i]);
    }
}


int main(void) {
    int n,m,i,q, u,v;
    scanf("%d %d",&n,&m);
    for(i=0;i<m;i++){
	scanf("%d %d",&u,&v);
	G[u].push_back(v);
	G[v].push_back(u);
    }
    dfs_init();
    /*
      ????????§?????¨???????????????
     */
    for(i=0; i<n; i++){
	if(labels[i]==0){
	    c++;
	    dfs2(i);
	}
    }

    scanf("%d",&q);
    for(i=0;i<q;i++){
	scanf("%d %d", &u, &v);
	if(labels[u]>0 && labels[u]==labels[v])printf("yes\n");
	else printf("no\n");
    }
    
    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
int d[100001];
int main(void){
	int	n,m;
	int s,t;
	int q;
	int i,j;
	int x,y;
	int cnt;
	vector<int>v[100001];
	queue<int>que;
	cin>>n>>m;
	for(i=0;i<m;i++){
		cin>>s>>t;
		v[s].push_back(t);
		v[t].push_back(s);
	}
	for(i=0;i<n;i++)	d[i]=0;
	cnt=0;
	for(i=0;i<n;i++){
		if(d[i]==0){
			cnt++;
			d[i]=cnt;
			que.push(i);
			while(!que.empty()){
				x=que.front();
				que.pop();
				for(j=0;j<v[x].size();j++){
					y=v[x][j];
					if(d[y]==0){
						d[y]=cnt;
						que.push(y);
					}
				}
			}
		}
	}
	cin>>q;
	for(i=0;i<q;i++){
		cin>>s>>t;
		cout<<((d[s]==d[t])?"yes":"no")<<endl;
	}
	
	return 0;
}

C++: #include <stdio.h>
#include <iostream>
#include <vector>
#include <queue>
using namespace std;

#define MAX_N 100000
#define MAX_M 100000
#define WHITE 1
#define GREY 2
#define BLACK 3

vector<int> G[MAX_N];
int V[MAX_N];
int V_num[MAX_N];

void init(void){
    for(int i = 0; i < MAX_N; i++){
        V[i] = WHITE;
        V_num[i] = i;
    }
}

void labeling(int target){
    queue<int> Q;
    Q.push(target);
    while(!Q.empty()){
        int num = Q.front(); Q.pop();
        for(int i = 0; i < G[num].size(); i++){
            if(V[G[num][i]] == WHITE){
                Q.push(G[num][i]);
                V[G[num][i]] = GREY;
                V_num[G[num][i]] = target;
            }
        }
        V[num] = BLACK;
    }
}

int main(void){
    init();
    int n, m;
    scanf("%d %d\n", &n, &m);
    for(int i = 0; i < m; i++){
        int a, b;
        scanf("%d %d", &a, &b);
        G[a].push_back(b);
        G[b].push_back(a);
    }

    for(int i = 0; i < n; i++){
        if(V[i] != WHITE){
            continue;
        }
        labeling(i);
    }

    int q;
    scanf("%d", &q);
    for(int i = 0; i < q; i++){
        int a, b;
        scanf("%d %d", &a, &b);
        if(V_num[a] == V_num[b]){
            printf("yes\n");
        }else{
            printf("no\n");
        }
    }

    /*
    for(int i = 0; i < n; i++){
        printf("%d %d\n", i, V_num[i]);
    }
    */
}

C++: // ALDS1_11_D.cpp
// Graph I - Connected Components

#include <iostream>
#include <vector>
#include <queue>
using namespace std;

void bfs(vector<vector<int>> &sns, vector<int> &arrived, int x, int y)
{
    if (arrived[y] != 0) return;
    queue<int> mq;
    mq.push(x);
    while(!mq.empty()) {
        int curr = mq.front();
        mq.pop();
        arrived[curr] = 2;
        for (int i = 0; i < sns[curr].size(); i++) {
            int next = sns[curr][i];
            if (arrived[next] == 0) {
                mq.push(next);
                arrived[next] = 1;
            }
        }
    }
}

int main()
{
    freopen("ALDS1_11_D_in22.txt", "r", stdin);
    freopen("out22.txt", "w", stdout);
    int m, n, q;
    cin >> n >> m;
    vector<vector<int> > sns(n, vector<int>());
    int x, y;
    for (int i = 0; i < m; i++) {
        cin >> x >> y;
        sns[x].push_back(y);
        sns[y].push_back(x);
    }

    cin >> q;
    while (q--) {
        vector<int> arrived(n);
        cin >> x >> y;
        bfs(sns, arrived, x, y);
        if (arrived[y]) cout << "yes" << endl;
        else cout << "no" << endl;
    }
    return 0;
}