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

  return 0;
}

C++: #include <cstdio>
#include <cstdlib>
#include <queue>
using namespace std;

int n;
bool **connection;

bool isFriend(int s, int t){
    int i;
    bool f[n];
    for(i=0;i<n;i++)f[i]=false;
    f[s]=true;
    int u;
    queue<int> q;
    q.push(s);
    while(!q.empty()){
        u=q.front();q.pop();
        for(i=0;i<n;i++){
            if(connection[u][i]&&f[i]==false){
                connection[u][i]=true;
                connection[i][u]=true;
                if(i==t)return true;
                f[i]=true;
                q.push(i);
            }
        }
    }
    return false;
}

int main(){
    int i, j, m, s, t, q;
    scanf("%d %d",&n,&m);
    connection = (bool **)malloc(sizeof(bool *)*n);
    for(i=0;i<n;i++){
        connection[i] = (bool *)malloc(sizeof(bool)*n);
        for(j=0;j<n;j++){
            connection[i][j]=0;
        }
    }
    for(i=0;i<m;i++){
        scanf("%d %d",&s,&t);
        connection[s][t]=true;
        connection[t][s]=true;
    }
    scanf("%d",&q);
    for(i=0;i<q;i++){
        scanf("%d %d",&s,&t);
        if(isFriend(s,t))printf("yes\n");
        else printf("no\n");
    }
    return 0;
}

C++: #define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;

//#define int long long
#define DBG 1
#define dump(o) if(DBG){cerr<<#o<<" "<<o<<endl;}
#define dumpc(o) if(DBG){cerr<<#o; for(auto &e:(o))cerr<<" "<<e;cerr<<endl;}
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define each(it,c) for(auto it=(c).begin();it!=(c).end();it++)
#define all(c) c.begin(),c.end()
const int INF = sizeof(int) == sizeof(long long) ? 0x3f3f3f3f3f3f3f3fLL : 0x3f3f3f3f;
const int MOD = (int)(1e9 + 7);
vector<vector<int>>vec;
int n;
vector<int>color;
void bsf(int s,int c) {
	queue<int>q;
	q.push(s);
	color[s] = c;
	while (!q.empty()) {
		int u = q.front(); q.pop();
		rep(v, 0, vec[u].size()) {
			if (color[vec[u][v]] != -1)continue;
			color[vec[u][v]] = c;
			q.push(vec[u][v]);
		}
	}
}
void solve() {
	rep(i, 0, n) {
		if (color[i] == -1)bsf(i, i);
	}
}
signed main() {
	cin >> n; vec = vector<vector<int>>(n); color = vector<int>(n, -1);
	int m; cin >> m;
	rep(i, 0, m) {
		int s, t; cin >> s >> t;
		vec[s].push_back(t);
		vec[t].push_back(s);
	}
	solve();
	int q; cin >> q;
	rep(i, 0, q) {
		int s, t; cin >> s >> t;
		if (color[s] == color[t])cout << "YES" << endl;
		else cout << "NO" << endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)
#define len(x) ((int)(x).size())
#define mp make_pair
#define eb emplace_back
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;
constexpr int MAX = 1e6;
constexpr int NIL = -1;
int n;
vector<vi> G(MAX);
vi color(MAX, NIL), S;
inline void dfs(int r, int c) {
	S.eb(r);
	color[r] = c;
	int u, v;
	while(!S.empty()) {
		u = S.back(); S.pop_back();
		rep(i, 0, len(G[u])) {
			v = G[u][i];
			if(color[v] == NIL) {
				color[v] = c;
				S.eb(v);
			}
		}
	}
}
inline void assignColor() {
	int id = 0;
	rep(u, 0, n) {
		if(color[u] == NIL) dfs(u, ++id);
	}
}
int main() {
	int m;
	cin >> n >> m;
	int s, t;
	rep(i, 0, m) {
		cin >> s >> t;
		G[s].eb(t);
		G[t].eb(s);
	}
	assignColor();
	int q; cin >> q;
	rep(i, 0, q) {
		cin >> s >> t;
		P(color[s] == color[t] ? "yes" : "no");
	}
	return 0;
}