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>
#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;
}

C++: #include<bits/stdc++.h>
//cout<<setprecision(1)<<fixed<<endl;
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int MAX_N=100000;
const int INF = 0x3f3f3f3f;
#define eps 1e-7
int n,m;
int e;
int begin[101010];
int next[101010];
int to[101010];
int vis[101010];
//bool search(int st,int ed){
//	queue<int> q;
//	q.push(st);
//	q.push(ed);
//	vis[st]=1;
//	while(!q.empty()){
//		int now=q.front();
//		q.pop();
//		int te=begin[now];
//		while(te!=-1){
//			if(to[te]==ed)
//				return true;
//			if(vis[to[te]]==0){
//				q.push(to[te]);
//				vis[to[te]]=1;
//			}
//			te=next[te];
//		}
//	}
//	return false;
//}

bool doublesearch(int st,int ed){
	int size1=1;
	int size2=1;
	queue<int> q[2];
	q[0].push(st);
	q[1].push(ed);
	vis[st]=1;
	vis[ed]=2;
	while((!q[0].empty())&&(!q[1].empty())){
		if(size1<=size2){
			int now=q[0].front();
			q[0].pop();
			int te=begin[now];
			while(te!=-1){
				if(vis[to[te]]==2)
					return true;
				if(vis[to[te]]==0){
					q[0].push(to[te]);
					vis[to[te]]=1;
				}
				te=next[te];
			}
		}
		else{
			int now=q[1].front();
			q[1].pop();
			int te=begin[now];
			while(te!=-1){
				if(vis[to[te]]==1)
					return true;
				if(vis[to[te]]==0){
					q[1].push(to[te]);
					vis[to[te]]=1;
				}
				te=next[te];
			}
		}
	}
	return false;
}
int main(){
	ios::sync_with_stdio(false);
	int n,m,q;
	int st,ed;
	while(scanf("%d%d",&n,&m)!=EOF){
		memset(begin,-1,sizeof(begin));
		memset(next,-1,sizeof(next));
		memset(to,-1,sizeof(to));
		e=0;
		for(int i=0;i<m;i++){
			scanf("%d%d",&st,&ed);
			to[++e]=ed;
			next[e]=begin[st];
			begin[st]=e;
			to[++e]=st;
			next[e]=begin[ed];
			begin[ed]=e;
		}
		scanf("%d",&q);
		for(int i=0;i<q;i++){
			memset(vis,0,sizeof(vis));
			scanf("%d%d",&st,&ed);
			if(doublesearch(st,ed))
				printf("yes\n");
			else
				printf("no\n");
		}
	}

	return 0;
}

C++: #include<iostream>
#include<queue>
#include<vector>
#include<cstring>
using namespace std;
queue<int>Q; int x[200000], n, m, q, s, t, p; vector<int>a[200000];

bool bfs(int A,int B) {
	memset(x, 0, sizeof(x));
	x[A] = 1;
	Q.push(A);
	while (!Q.empty()) {
		for (int k = 0; k < a[Q.front()].size(); k++) {
			p = x[a[Q.front()][k]];
			if (x[p] == 0) { 
				Q.push(a[Q.front()][k]);
			}
		}
		Q.pop();
	}
	if (x[B] == 1) {
		return true;
	}
	else {
		return false;
	}
}

int main() {
	cin >> n >> m;
	for (int i = 0; i < m; i++) {
		cin >> s >> t;
		a[s].push_back(t);
		a[t].push_back(s);
	}
	cin >> q;
	for (int i = 0; i < q; i++) {
		cin >> s >> t;
		if (bfs(s, t)) { cout << "yes" << endl; }
		else { cout << "no" << endl; }
	}
	return 0;
}