Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

const MAX = 100000

type Queue struct {
	head      int
	tail      int
	container [MAX]int
}

func (q *Queue) push(n int) {
	q.container[q.tail] = n
	q.tail = (q.tail + 1) % MAX
}

func (q *Queue) pop() int {
	res := q.container[q.head]
	q.head = (q.head + 1) % MAX
	return res
}

func (q *Queue) isEmpty() bool {
	return q.head == q.tail
}

var sc = bufio.NewScanner(os.Stdin)
var route [][]int
var SEEN [MAX]bool
var GROUP [MAX]int

func scanInt() int {
	num, _ := strconv.Atoi(scanString())
	return num
}

func scanString() string {
	sc.Scan()
	return sc.Text()
}

func init() {
	sc.Split(bufio.ScanWords)
}

func bfs(start, group int) {
	que := Queue{}
	que.push(start)

	for !que.isEmpty() {
		id := que.pop()

		if SEEN[id] {
			continue
		}
		SEEN[id] = true
		GROUP[id] = group

		for _, next := range route[id] {
			que.push(next)
		}
	}
}

func main() {
	n, m := scanInt(), scanInt()
	route = make([][]int, n)
	for i := 0; i < m; i++ {
		s, t := scanInt(), scanInt()
		route[s] = append(route[s], t)
		route[t] = append(route[t], s)
	}

	for i := 0; i < n; i++ {
		if !SEEN[i] {
			bfs(i, i+1)
		}
	}

	w := bufio.NewWriter(os.Stdout)
	q := scanInt()
	for i := 0; i < q; i++ {
		s, t := scanInt(), scanInt()
		if GROUP[s] == GROUP[t] {
			fmt.Fprintln(w, "yes")
		} else {
			fmt.Fprintln(w, "no")
		}
	}
	w.Flush()
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)

int MAX = 100000;

vector<vector<int>> user(MAX, vector<int>(0));
vector<int> group(MAX, -1);

// 模範回答
// void dfs(int start, int group_i) {
//     stack<int> s;
//     group[start] = group_i;
//     s.push(start);
//     while (!s.empty()) {
//         int current = s.top();
//         s.pop();
//         for (int i = 0; i < user[current].size(); i++) {
//             int adj = user[current][i];
//             if (group[adj] == NIL) {
//                 s.push(adj);
//                 group[adj] = group_i;
//             }
//         }
//     }
// }

// 再帰によるdfs
void dfs(int start, int group_i) {
    group[start] = group_i;
    rep(i, user[start].size()) {
        int adj = user[start][i];
        if (group[adj] == -1) {
            dfs(adj, group_i);
        }
    }
}

// スタックによるdfsパターン1
// void dfs(int start, int group_i) {
//     stack<int> s;
//     group[start] = group_i;
//     s.push(start);
//     while (!s.empty()) {
//         int current = s.top();
//         group[current] = group_i;
//         bool stop = true;
//         for (int i = 0; i < user[current].size(); i++) {
//             int adj = user[current][i];
//             if (group[adj] == -1) {
//                 s.push(adj);
//                 stop = false;
//                 break;
//             }
//         }
//         if (stop) s.pop();
//     }
// }

int main() {
    int n, m, s, t, q;
    scanf("%d %d", &n, &m);
    rep(i, m) {
        scanf("%d %d", &s, &t);
        user[s].push_back(t);
        user[t].push_back(s);
    }

    int group_i = 0;
    rep(i, n) {
        if (group[i] == -1) {
            dfs(i, group_i++);
        }
    }

    scanf("%d", &q);
    rep(i, q) {
        scanf("%d %d", &s, &t);
        if (group[s] == group[t]) printf("yes\n");
        else printf("no\n");
    }
}

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

using namespace std;

void dfs(vector<vector<int>>& g, vector<int>& color, int id, int c) {
    stack<int> s;
    vector<bool> visited(g.size(), false);
    s.push(id);
    color[id] = c;
    while (!s.empty()) {
        int id = s.top();
        s.pop();
        visited[id] = true;

        for (int i = 0; i < g[id].size(); ++i) {
            int adj = g[id][i];
            if (!visited[adj]) {
                color[adj] = c;
                s.push(adj);
            }
        }
    }
}

void assign_colors(vector<vector<int>>& g, vector<int>& color) {
    int color_id = 1;
    for (int i = 0; i < g.size(); ++i) {
        if (color[i] == -1) {
            dfs(g, color, i, color_id);
            ++color_id;
        }
    }
}

int main() {
    ios::sync_with_stdio(false);

    int n, m;
    cin >> n >> m;

    vector<vector<int>> g(n);
    for (int i = 0; i < m; ++i) {
        int p1, p2;
        cin >> p1 >> p2;
        g[p1].push_back(p2);
        g[p2].push_back(p1);
    }

    vector<int> color(n, -1);
    assign_colors(g, color);

    int p;
    cin >> p;
    for (int i = 0; i < p; ++i) {
        int p1, p2;
        cin >> p1 >> p2;
        if (color[p1] == color[p2])
            cout << "yes\n";
        else
            cout << "no\n";
    }
}

C++: #include <iostream>
#include <queue>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <climits>
using namespace std;

int n;

vector<int> uf;

void initialize(int n)
{
  uf = vector<int>(n);
  for (int i = 0; i < n; i++)
    uf[i] = i;
}

int root(int i)
{
  if (uf[i] == i) return i;
  return uf[i] = root(uf[i]);
}

void unite(int i, int j)
{
  int ri = root(i);
  int rj = root(j);
  if (ri != rj)
    uf[rj] = ri;
}

bool same(int i, int j)
{
  return root(i) == root(j);
}

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

  initialize(n);
  for (int i = 0; i < m; i++) {
    int u, v; cin >> u >> v;
    unite(u, v);
  }

  cin >> q;
  for (int i = 0; i < q; i++) {
    int u, v; cin >> u >> v;
    cout << (same(u, v)?"yes":"no") << endl;
  }

  return EXIT_SUCCESS;
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <utility>
#include <queue>
#include <stack>
#include <string>
#include <climits>
using namespace std;

#define MAX_N  100000
#define MAX_M  100000
#define MAX_Q  10000

int n, m, q, k, kind[MAX_N] = {};
queue<int> Q;

void bf(vector<vector<int> >& sns, int s)
{
    Q.push(s);
    while (!Q.empty()) {
        s = Q.front();
        Q.pop();
        kind[s] = k;
        for (int i = 0; i < sns[s].size(); i++) {
            if (!kind[sns[s][i]]) Q.push(sns[s][i]);
        }
    }
}

int main()
{
    cin >> n >> m;
    vector<vector<int> > sns(n);
    int s, d;
    while (m--) {
        cin >> s >> d;
        sns.at(s).push_back(d);
        sns.at(d).push_back(s);
    }
    k = 0;
    for (int s = 0; s < n; s++) {
        if (!kind[s]) {
            k++;
            bf(sns, s);
        }
    }
    cin >> q;
    while (q--) {
        cin >> s >> d;
        cout << (kind[s] == kind[d] ? "yes" : "no") << endl;
    }
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, start, n) for (int i = (int)(start); i < (int)(n); ++i)
void search(vector<vector<int> > &G, int *color, int s, int id)
{
    color[s] = id; //sは訪問済み
    stack<int> q;
    q.push(s);
    while (q.empty() == false)
    {
        int p = q.top();
        q.pop();
        rep(i, 0, G[p].size())
        {
            int new_p = G[p][i];
            if (color[new_p] == 0)
            {
                color[new_p] = id;
                q.push(new_p);
            }
        }
    }
}
int main()
{
    int n, m;
    cin >> n >> m;
    vector<vector<int> > G(n, vector<int>(0));
    int color[n] = {};
    int s, t;
    rep(i, 0, m)
    {
        scanf("%d %d", &s, &t);
        G[s].push_back(t);
        G[t].push_back(s);
    }
    int id(0);
    rep(i, 0, n)
    {
        if (color[i] == 0)
        {
            search(G, color, i, ++id);
        }
    }
    int q;
    cin >> q;
    rep(i, 0, q)
    {
        scanf("%d %d", &s, &t);
        if (color[s] == color[t])
            printf("yes\n");
        else
            printf("no\n");
    }
}