Go: package main

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

func main() {
	var n,m int
	fmt.Scan(&n)
	group := make([]int, n)
	g := make([][]int, n)
	for i := 0; i < n; i++ {
		g[i] = []int{}
		group[i] = -1
	}
	
	fmt.Scan(&m)
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	for i := 0; i < m; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		
		g[s] = append(g[s], t)
		g[t] = append(g[t], s)
	}
	for i := 0; i < n; i++ {
		if group[i] != -1 {
			continue
		}
		q := []int{i}
		for len(q) > 0 {
			pop := q[0]
			if len(q) > 1 {
				q = q[1:]
			} else {
				q = []int{}
			}
			if group[pop] == -1 {
				q = append(q, g[pop]...)
				group[pop] = i
			}
		}
	}
	sc.Scan()
	q, _ := strconv.Atoi(sc.Text())
	for i := 0; i < q; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())

		if group[s] == group[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func root(i int, group *[]int) int {
	if i == (*group)[i] {
		return i
	}
	(*group)[i] = root((*group)[i], group)
	return (*group)[i]
}

C++: #include <cstdio>
#include <set>
#include <queue>
#include <vector>

void assignGroup(const std::vector<std::set<int>>& firend_relationships, std::vector<int>& group)
{
  int current_group = 1;
  std::queue<int> next_queue;
  std::set<int> searched_set;

  for (int i = 0; i < (int)firend_relationships.size(); ++i)
  {
    // Any group is the id assigned, then skip it
    if (searched_set.count(i) != 0)
      continue;

    group[i] = current_group;
    next_queue.push(i);

    while (!next_queue.empty())
    {
      // Remove from waiting list
      int current_id = next_queue.front();
      next_queue.pop();
      // Add to searched list
      searched_set.insert(current_id);

      // Add to waiting list which is not serached yet
      std::set<int>::const_iterator itr;
      for (itr = firend_relationships[current_id].begin();
           itr != firend_relationships[current_id].end();
           ++itr)
      {
        // Ignore searched ones
        if (searched_set.count(*itr) != 0)
          continue;

        group[*itr] = current_group;
        next_queue.push(*itr);
      }
    }

    // Assign the different group number
    ++current_group;
  }
}

bool isConnected(const int& id_from, const int& id_to, const std::vector<int>& group)
{
  return group[id_from] == group[id_to];
}

int main()
{
  int n, m;
  scanf("%d%d", &n, &m);

  std::vector<std::set<int>> firend_relationships;
  std::vector<int> group;
  firend_relationships.resize(n);
  group.resize(n);
  for (int i = 0; i < m; ++i)
  {
    int id1, id2;
    scanf("%d%d", &id1, &id2);
    firend_relationships[id1].insert(id2);
    firend_relationships[id2].insert(id1);
  }

  assignGroup(firend_relationships, group);

  int q;
  scanf("%d", &q);
  for (int i = 0; i < q; ++i)
  {
    int id1, id2;
    scanf("%d%d", &id1, &id2);
    if (isConnected(id1, id2, group))
      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) dfs(u,id++);
    }
    }

int main() {
    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++: #include <iostream>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <string>
#include <cctype>
#include <stack>
#include <queue>
#include <vector>
#include <cstdlib>
#include <list>
#define _USE_MATH_DEFINES
#include <math.h>

using namespace std;

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

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

void assignColor();
void dfs(int r, int c);

int main() {

	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;
}

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)
			dfs(u, id++);
	}
		
}

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);
			}
		}
	}
}