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<climits>
#include<vector>
#include<list>
#include<functional>
#include<algorithm>
#include<string>
#include<cmath>
#include<complex>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<tuple>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) for(int i=0;i<(n);i++)
#define INF (int)1e9
#define INFL (ll)1e11
using namespace std;
typedef long long ll;

typedef pair<int, int> P;

vector<vector<int>> a(100000);
vector<int> comp(100000, 0);

void dfs(int s, int id) {
	stack<int> st;
	st.push(s);
	comp[s] = id;
	while (!st.empty()) {
		int i = st.top();
		int k = a[i].size();
		REP(j, k + 1) {
			if (j < k) {
				int t = a[i][j];
				if (comp[t] != id) {
					comp[t] = id;
					st.push(t);
					break;
				}
			}
			else st.pop();
		}
	}
}

void divide(int size) {
	int s = 0;
	int id = 1;
	while (1) {
		dfs(s, id);
		while (s < size && comp[s]>0) s++;
		if (s == size) break;
		id++;
	}
	return;
}

int main() {
	//cin.tie(0);
	//ios::sync_with_stdio(false);

	int n, m;
	scanf("%d %d", &n, &m);
	//cin >> n >> m;
	REP(i, m) {
		int s, t;
		scanf("%d %d", &s, &t);
		//cin >> s >> t;
		a[s].push_back(t);
		a[t].push_back(s);
	}
	int q;
	cin >> q;
	divide(n);
	REP(i, q) {
		int s, t;
		scanf("%d %d", &s, &t);
		//cin >> s >> t;
		if (comp[s] == comp[t]) printf("yes\n");
		else printf("no\n");
	}

	return 0;
}

C++: #include<bits/stdc++.h>
#define same(a,b) (find(a)==find(b))
#define uni(a,b) fa[find(a)]=find(b)
#define init(n) for(int i=0;i<n;i++) fa[i]=i

int fa[100100];

int find(int x)
{
	if(x==fa[x]) return x;
	return fa[x]=find(fa[x]);
}

int main()
{
	int n,m;
	scanf("%d%d",&n,&m);
	init(n);
	for(int i=0;i<m;i++)
	{
		int u,v;
		scanf("%d%d",&u,&v);
		uni(u,v);
	}
	int q;
	scanf("%d",&q);
	for(int i=0;i<q;i++)
	{
		int u,v;
		scanf("%d%d",&u,&v);
		if(same(u,v)) printf("yes\n");
		else printf("no\n");
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;
static const int MAX = 100000;
static const int NIL = -1;

int n;
vector<int> G[MAX];
int color[MAX];

void dfs(int r, int c){
  stack<int> S;
  S.push(r);
  color[r] = c;
  while( !S.empty()) {
   int u = S.top(); S.pop();
   for(int i = 0; i < G[u].size(); i++){
    int v = G[u][i];
   if(color[v] == NIL){
    color[v] = c;
    S.push(v);
    }
   }
  }
 }
  
void assignColor(){
  int id = 1;
  for ( int i = 0; i < n; i++) color[i] = NIL;
  for ( int u = 0; u < n; u++) {
    if ( color[u] == NIL) des(u,id++);
  }
 }
int main (){
  int s,t,q,m;

  cin >> n >> m;

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

 assignColor();

 cin >> q;

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

C++: #include <stdio.h>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <math.h>
#include <queue>
#include <string.h>
#include <stdlib.h>
#include <map>
#include <set>
using namespace std;
typedef unsigned long long ull;
typedef  long long ll;
class UnionFind {
public:
	vector<int> Parent;
	UnionFind(int N) {
		Parent = vector<int>(N, -1);
	}
	int root(int A) {
		if (Parent[A] < 0) {
			return A;
		}
		return Parent[A] = root(Parent[A]);
	}

	int size(int A) {
		return -Parent[root(A)];
	}

	bool connect(int A, int B) {
		A = root(A);
		B = root(B);
		if (A == B) {
			return false;
		}
		if (size(A) < size(B)) {
			swap(A, B);
		}

		Parent[A] += Parent[B];
		Parent[B] = A;

		return true;
	}

};
int main()
{
	int n, m, q;
	cin >> n >> m;
	UnionFind uni(n);
	for (int i = 0; i < m; i++) {
		int s, t;
		cin >> s >> t;
		uni.connect(s, t);
	}
	cin >> q;
	for (int i = 0; i < q; i++) {
		int s, t;
		cin >> s >> t;
		if (uni.root(s) == uni.root(t)) {
			cout << "yes" << endl;
		}
		else {
			cout << "no" << endl;
		}
	}

	return 0;
}

C++: #include <cstdio>
#include <vector>
#include <queue>
#include <algorithm>
#include <iterator>
using namespace std;

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

int bfs(int s, int t) {
    vector<int> *vc = new vector<int>[n];
    for (int i = 0; i < n; i++) {
        vc[i] = v[i];
    }

    queue<int> q;
    q.push(s);
    for (int i = 0; i < n; i++) {
        int u = q.front();
        q.pop();
        for (vector<int>::iterator it = vc[i].begin(); it != vc[i].end(); it++) {
            if (*it == t) {
                return 1;
            }
            q.push(*it);
            vector<int>::iterator result = find(vc[*it].begin(), vc[*it].end(), i);
            if (result != vc[*it].end()) { vc[*it].erase(result); }
        }
    }
    return 0;
}

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);
    }

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

    return 0;
}