Go: package main

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

var (
	n     int
	G     [100000][]int
	color [100000]*int
)

func dfs(r int, c int) {
	S := Stack{}
	S.Push(r)
	color[r] = &c
	for !S.IsEmpty() {
		u := S.Pop()
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == nil {
				color[v] = &c
				S.Push(v)
			}
		}
	}
}

func assignColor() {
	id := 1
	for i := 0; i < n; i++ {
		color[i] = nil
	}
	for u := 0; u < n; u++ {
		if color[u] == nil {
			id++
			dfs(u, id)
		}
	}
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan()
	n, _ = strconv.Atoi(sc.Text())
	sc.Scan()
	r, _ := strconv.Atoi(sc.Text())

	for i := 0; i < r; 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)
	}
	assignColor()
	sc.Scan()
	qNum, _ := strconv.Atoi(sc.Text())
	for i := 0; i < qNum; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

// Stack is Stack
type Stack struct {
	stack []int
}

// Push new value
func (stack *Stack) Push(val int) {
	stack.stack = append(stack.stack, val)
}

// Pop new value
func (stack *Stack) Pop() int {
	val := stack.stack[len(stack.stack)-1]
	stack.stack = stack.stack[0 : len(stack.stack)-1]
	return val
}

// IsEmpty return true when stack is empty
func (stack *Stack) IsEmpty() bool {
	return len(stack.stack) == 0
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;
const int maxn = 100001;

vector<int> G[maxn];
int vis[maxn];

void DFS(int u, int k)
{
    vis[u] = k;
    for(vector<int>::iterator it = G[u].begin(); it != G[u].end(); it++)
        if(vis[*it] == -1)
            DFS(*it, k);
}

int main()
{
    int n, m;
    cin >> n >> m;
    for(int i = 0; i < m; i++)
    {
        int x, y;
        cin >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    for(int j = 0; j < n; j++)
            vis[j] = -1;
    for(int i = 0; i < n; i++)
        if(vis[i] == -1)
            DFS(i, i);
    int q;
    cin >> q;
    for(int i = 0; i < q; i++)
    {
        int x, y;
        cin >> x >> y;
        if(vis[y] == vis[x])
            cout << "yes" <<endl;
        else
            cout << "no" <<endl;
    }
    return 0;
}

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<int> went(n.size(), 0);

	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] = 1;
			}
		}
	}
	return false;
}

void color(std::vector<std::vector<int> > n) {
	std::vector<int> color(n.size(), 0);
	std::vector<int> went(n.size(), 0);
	std::stack<int> s;

	int count = 1;
	for (size_t i = 0; i < n.size(); i++) {
		if (color[i] != 0) continue;
		s.push(i);
		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 (!went[*it]) {
					s.push(*it);
					went[*it] = 1;
					color[*it] = count;
				}
			}
		}
		count++;
	}
	int question;
	std::cin >> question;
	for (int i = 0; i < question; i++) {
		int from, to;
		std::cin >> from >> to;
		if (color[from] == color[to]) {
			std::cout << "yes" << std::endl;
		} else {
			std::cout << "no" << std::endl;
		}
	}

}

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);
	}

	color(n);

	return 0;
}

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

#include<stdio.h>


#include<queue>
using namespace std;
int main()
{
    int person_number,relation_number;

    cin>>person_number>>relation_number;

    vector<vector<int > > list(person_number);
    for(int i=0;i<relation_number;i++)
    {
        int start,end;
        scanf("%d %d ",&start,end);
        int flag=0;
        for(auto n:list[start])
        {
            if(n==end)
                flag=1;
        }
        if(flag==0) 
        {
            list[start].push_back(end);
            list[end].push_back(start);
        }
    }

    int test_number;
    scanf("%d",&test_number);
for(int i=0;i<test_number;i++)
{
    int from,to;
    scanf("%d %d ",&from,&to);
    queue<int> q;
    q.push(from);
    vector<int> ban_list;
    for(int i=0;i<person_number;i++)
    {
        ban_list.push_back(0);
    }
    ban_list[from]=1;
    for(;!q.empty();q.pop())
    {
        int flag=0;
        for(auto n:list[q.front()])
        {
            if(n==to) 
            { 
                flag=1;
                break;
            }
            if(ban_list[n]==0)
            {
                ban_list[n]=1;
                q.push(n);
            }
        }
        if(flag==1) break;
    }
    if(!q.empty()) cout<<"yes"<<endl;
    else cout<<"no"<<endl;
}
    return 0;
}

C++: #include <iostream>
using namespace std;

const int MAX_V = 100010;
int par[MAX_V];
int treerank[MAX_V];

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

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

void unite(int x, int y){
  x = find(x);
  y = find(y);
  if(x == y) return;
  if(treerank[x] < treerank[y]){
    par[x] = y;
  }
  else{
    par[y] = x;
    if(treerank[x] == treerank[y]) treerank[x]++;
  }
}

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

int main(){
  int n, m; cin >> n >> m;
  init(n);
  for(int i=0; i<m; i++){
    int s, t; cin >> s >> t;
    unite(s, t);
  }
  int q; cin >> q;
  for(int i=0; i<q; i++){
    int s, t; cin >> s >> t;
    cout << (same(s, t) ? "yes" : "no") << endl;
  }
}