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<vector>
#include<stack>
#include<algorithm>

bool dfs(std::vector<std::vector<int> > n, int from, int to) {
	std::stack<int> s;
	std::vector<bool> went(n.size(), false);

	s.push(from);
	while (s.size() != 0){
		int num = s.top(); s.pop();
		for (std::vector<int>::iterator it = n[num].begin(); it != n[num].end(); it++) {
			if (*it == to) return true;
			if (!went[*it]) {
				s.push(*it);
				went[*it] = true;
			}
		}
	}
	return false;
}

int main() {
	int people, relation;

	std::cin >> people >> relation;

	std::vector<std::vector<int> > n(people);

	for (int i = 0; i < relation; i++) {
		int from, to;
		std::cin >> from >> to;
		n[from].push_back(to);
		n[to].push_back(from);
	}

	int question;
	std::cin >> question;
	for (int i = 0; i < question; i++) {
		int from, to;
		std::cin >> from >> to;
		if (dfs(n, from, to)) {
			std::cout << "yes" << std::endl;
		} else {
			std::cout << "no" << std::endl;
		}
	}

	return 0;
}

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

using namespace std;

#define MAX 10000

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]==-1)
			{
				color[v]=c;
				S.push(v);
			}
		}
	}
}

void assignColor()
{
	for (int i = 0; i < n; ++i)
	{
		color[i]=-1;
	}
	int id=1;
	for (int i = 0; i < n; ++i)
	{
		if (color[i]==-1)
		{
			dfs(i,id++);
		}
	}
}

int main(int argc, char const *argv[])
{
	int s,t,m,q;
	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++: #define _USE_MATH_DEFINES
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <clocale>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#define IOS ios::sync_with_stdio(false); cin.tie(0);
#define FOR(i, s, n) for(int i = (s), i##_len=(n); i < i##_len; ++i)
#define FORS(i, s, n) for(int i = (s), i##_len=(n); i <= i##_len; ++i)
#define VFOR(i, s, n) for(int i = (s); i < (n); ++i)
#define VFORS(i, s, n) for(int i = (s); i <= (n); ++i)
#define REP(i, n) FOR(i, 0, n)
#define REPS(i, n) FORS(i, 0, n)
#define VREP(i, n) VFOR(i, 0, n)
#define VREPS(i, n) VFORS(i, 0, n)
#define RFOR(i, s, n) for(int i = (s), i##_len=(n); i >= i##_len; --i)
#define RFORS(i, s, n) for(int i = (s), i##_len=(n); i > i##_len; --i)
#define RREP(i, n) RFOR(i, n, 0)
#define RREPS(i, n) RFORS(i, n, 0)
#define ALL(v) (v).begin(), (v).end()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(ALL(v), greater<decltype(v[0])>())
#define SZ(x) ((int)(x).size())
#define PB push_back
#define MP make_pair
#define MT make_tuple
#define BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(ALL(v)), v.end())

using ll = long long;
using Pi_i = pair<int, int>;
using VB = vector<bool>;
using VC = vector<char>;
using VD = vector<double>;
using VI = vector<int>;
using VLL = vector<ll>;
using VS = vector<string>;
using VSH = vector<short>;

const int MOD = 1000000007;
const int INF = 1000000000;
const int NIL = -1;

template<class T, class S>
bool chmax(T &a, const S &b){
    if(a < b){
        a = b; return true;
    }
    return false;
}
template<class T, class S>
bool chmin(T &a, const S &b){
    if(b < a){
        a = b; return true;
    }
    return false;
}


class UnionFind{
    vector<int> par;
    vector<int> rank;

public:
    UnionFind(){}
    UnionFind(int n): par(n), rank(n){
        REP(i, n){
            par[i] = i;
            rank[i] = 0;
        }
    }

    void resize(int n){
        int m = par.size();
        par.resize(n);
        rank.resize(n, 0);
        FOR(i, m, n) par[i] = i;
    }

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

    void unit(int x, int y){
        x = find(x);
        y = find(y);
        if(x == y) return;

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

    bool same(int x, int y){
        return find(x) == find(y);
    }
};
int n;
UnionFind UF;
vector<VI> edge;
VB visited;

void dfs(int u){
    visited[u] = true;
    for(int v: edge[u]){
        if(!visited[v]){
            UF.unit(u, v);
            dfs(v);
        }
    }
}

int main(){
    int m; cin >> n >> m;
    edge.resize(n);
    visited.resize(n, false);
    REP(i, m){
        int u, v; cin >> u >> v;
        edge[u].PB(v); edge[v].PB(u);
    }
    UF.resize(n);
    REP(i, n){
        if(!visited[i]) dfs(i);
    }
    int q; cin >> q;
    REP(i, q){
        int s, t; cin >> s >> t;
        cout << (UF.same(s, t) ? "yes" : "no") << "\n";
    }
    return 0;
}