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 <cctype>
#include <vector>
using namespace std;

#define si static inline
#define gcu getchar_unlocked
si int in() {
	int c, n = 0;
	//bool minus = false;
	//if ((c = gcu()) == '-') minus = true; else ungetc(c, stdin);
	while ((c = gcu()) >= '0' && c <= '9') n = 10 * n + (c - '0');
	return n; }
	//return minus ? -n : n; }
si void scan(char *s) {while (!isspace(*s++ = gcu()));}
#define pcu putchar_unlocked
#define svo si void out
template <typename T>
svo(T n) {
	static char buf[20];
	char *p = buf;
	//if(n < 0) pcu('-'), n *= -1;
	if (!n) *p++ = '0';
	else while (n) *p++ = n % 10 + '0', n /= 10;
	while (p != buf) pcu(*--p); }
svo(const char *s){while(*s)pcu(*s++);}
svo(char *s){while(*s)pcu(*s++);}
svo(char c){pcu(c);}
template <typename T>
//svo(vector<T> &v){for(T &x:v)out(' '),out(x);out('\n');}
svo(vector<T> &v){for(T &x:v)out(&x == &v[0]?"":" "),out(x);out('\n');}
template <typename head, typename... tail>
svo(head&& h, tail&&... t){out(h);out(move(t)...);}

struct union_find {
	struct node {int p, r = 1;};
	vector<node> nodes;

	union_find(int n) : nodes(n) {
		int i = 0;
		for (node &n: nodes)
			n.p = i++;
	}
	int find(int x) {
		int &p = nodes[x].p;
		if (p == x)
			return x;
		else {
			p = find(p);
			return p;
		}
	}
	void unite(int a, int b) {
		int ar = find(a), br = find(b);
		node &an = nodes[ar], &bn = nodes[br];
		if (an.r > bn.r) {
			bn.p = ar;
			an.r += bn.r;
		} else if (ar != br) {
			an.p = br;
			bn.r += an.r;
		}
	}
	bool equal(int a, int b) {
		return find(a) == find(b);
	}
};

int main() {
	union_find u(in());
	int n = in();
	while(n--) {
		int a = in();
		u.unite(a, in());
	}
	int q = in();
	while (q--)
		out(u.equal(in(), in()) ? "yes" : "no", '\n');
}

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

#define MAX 100000

#define WHITE 0
#define GRAY 1
#define BLACK 2


using namespace std;

vector<int> G[MAX];
int graphc[MAX];
int color[MAX];
int colorCount;

void def(int o)
{
	int v;

	for (int i = 0; i < G[o].size(); i++) {

		v = G[o][i];
		if (color[v] == WHITE) {

			color[v] = GRAY;
			def(v);
		}
	}
	color[o] = BLACK;
	graphc[o] = colorCount;
}


int main(void)
{
	int n;
	int m;
	int s;
	int t;
	int q;


	cin >> n >> m;

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

	for (int i = 0; i < n; i++) {

		if (color[i] == WHITE) {
			colorCount++;
			def(n);
			
		}
	}

	cin >> q;

	for (int i = 0; i < q; i++) {

		cin >> s >> t;

		cout << ((graphc[s] == graphc[t]) ? "yes" : "no" )<< endl;
	}

	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define int long long

const int N = 1e5+10;
int par[N]; //親
int depth[N]; //木の深さ

struct UF{

  void init(int n){
    for(int i = 0; i < n; i++){
      par[i] = i;
      depth[i] = 0;
    }
  }

  //木の根を求める
  int root(int x){
    if(par[x] == x){
      return x;
    }
    else {
      return par[x] = root(par[x]);
    }
  }

  //xとyの属する集合を併合
  void unite(int x,int y){
    x = root(x);
    y = root(y);
    if(x == y) return;

    if(depth[x] < depth[y]) par[x] = y;
    else {
      par[y] = x;
      if(depth[x] == depth[y]) depth[x]++;
    }
  }
}uf;

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

  int n,m; cin >> n >> m;
  uf.init(n+1);
  for(int i = 0; i < m; i++){
    int x,y; cin >> x >> y;
    uf.unite(x,y);
  }

  int q; cin >> q;
  for(int i = 0; i < q; i++){
    int x,y; cin >> x >> y;
    if(uf.root(x) == uf.root(y)){
      cout << "yes" << endl;
    }
    else {
      cout << "no" << endl;
    }
  }

  return 0;
}

C++: #include <stdio.h>
#include <vector>
#include <algorithm>
#include <math.h>
#include <queue>

using namespace std;

int n,m,q,from,to;
int rank[100000],parent[100000];

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

bool isSame(int x,int y){
	return find(x) == find(y);
}

void unite(int x,int y){
	x = find(x);
	y = find(y);

	if(x == y)return;

	if(rank[x] < rank[y]){
		parent[x] = y;
	}else{
		parent[y] = x;
		if(rank[x] == rank[y])rank[x]++;
	}
}

int main(){

	scanf("%d %d",&n,&m);

	for(int i = 0; i < n; i++){
		rank[i] = 0;
		parent[i] = i;
	}

	for(int i = 0; i < m; i++){
		scanf("%d %d",&from,&to);

		if(isSame(from,to))continue;
		unite(from,to);
	}

	scanf("%d",&q);

	int left,right;

	for(int i = 0; i < q; i++){
		scanf("%d %d",&left,&right);

		if(isSame(left,right))printf("yes\n");
		else{
			printf("no\n");
		}
	}
	return 0;
}