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>

using namespace std;

#define N_MAX 100000

int search_connection(int s, int t);
vector<int> G[N_MAX], check_v;

int main()
{
    int n, m, i, s, t, q;

    cin >> n >> m;

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

    //??????????????????
    cin >> q;
    for (i = 0; i < q; i++) {
//        cout << "Q. " << i << endl;

        cin >> s >> t;

        if (check_v.size() != 0) check_v.clear();

        check_v.push_back(s);
        if ( search_connection(s, t) )
            cout << "yes" << endl;
        else
            cout << "no" << endl;
    }

    return 0;
}

int search_connection(int s, int t) {
    int i;
//    cout << "search " << s << ", " << t << endl;

    for (auto itr = G[s].begin(); itr != G[s].end(); itr++) {
        if (*itr == t) {
            return 1;
        }
        else if ( std::find(check_v.begin(), check_v.end(), *itr) != check_v.end() ) {
            //*itr?????¢?????¢?´¢??????node?????´??????????????¢?´¢????????????
        }
        else {
            //*itr???????????¢?´¢???????????????node?????´???
            check_v.push_back(*itr);
            if ( search_connection(*itr, t) )
                return 1;
        }
    }

    return 0;
}

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

using namespace std;

static const int N = 100;

int n, m;
int color[N], dist;

vector<int> G[N];

void dfs(int i, int c){
	queue<int> q; q.push(i);
	color[i] = c;

	while (!q.empty()) {
		int u = q.front(); q.pop();
		for (int i = 0; i < G[u].size(); ++i){
			int v = G[u][i];
			if (-1 == color[v]){
				color[v] = c;
				q.push(v);
			}
		}
	}
}


void search(){
	for (int i = 0; i < n; ++i) color[i] = -1;

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


int main()
{
	cin >> n >> m;

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

	search();

	cin >> n;
	for (int i = 0; i < n; ++i)
	{
		int u, v; cin >> u >> v;
		if (color[u] == color[v]) cout << "yes" << endl;
		else cout << "no" << endl;
	}

	return 0;
}

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

using namespace std;

static const int N = 100000;
static const int NIL = -1;

class ListGraph {
private:
    vector<int> Graph[N];
    int Group[N];
    int n;

public:
    ListGraph()
    {
        cin >> n;
        int m;
        cin >> m;
        int u, v;
        for(int i = 0; i < m; i++)
        {
            cin >> u >> v;
            Graph[u].push_back(v);
            Graph[v].push_back(u);
        }
    }

    void dfs(int start, int group)
    {
        stack<int> stack;
        stack.push(start);
        Group[start] = group;
        while(!stack.empty())
        {
            int u = stack.top();
            stack.pop();
            for(int i = 0; i < Graph[u].size(); i++) // uの全隣接頂点に対して
            {
                int v = Graph[u][i];
                if(Group[v] == NIL) // 未訪問(グループ未定)のとき
                {
                    Group[v] = group; // 自分のグループに含める
                    stack.push(v);
                }
            }
        }
    }

    void grouping()
    {
        int id = 1;
        for(int i = 0; i < n; i++)
            Group[i] = NIL;
        for(int u = 0; u < n; u++)
        {
            if(Group[u] == NIL)
                dfs(u, id++);
        }
    }

    string answer(int start, int goal)
    {
        if(Group[start] == Group[goal])
            return "yes";
        else
            return "no";
    }
};

int main()
{
    ListGraph graph;
    graph.grouping();
    int question;
    cin >> question;
    int start, goal;
    for(int i = 0; i < question; i++)
    {
        cin >> start >> goal;
        cout << graph.answer(start, goal) << endl;
    }
}