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 <queue>
using namespace std;
struct Info{
        int s;
        int t;
};
int main(){
        int N,M;
        cin >> N >> M;
        int groups[100000]={-1};
        for(int i=0 ; i<N ; i++ )
                groups[i]=-1;
        Info friends[100000];
        for(int i=0 ; i<M ; i++ )
                cin >> friends[i].s >> friends[i].t ;
        int group=0;
        for(int i=0 ; i<N ; i++ ){
                if(groups[i]!=-1)
                        continue;
                queue <int> cycle;
                cycle.push(i);
                while(cycle.size()!=0){
                        int now=cycle.front();cycle.pop();
                        for(int l=0 ; l<M ; l++ ){
                                if(now==friends[l].s)
                                        cycle.push(friends[l].t);
                        }
                        groups[now]=group;
                }
                group++;
        }
        cin >> N;
        for(int i=0 ; i<N ; i++ ){
                int s,t;
                cin >> s>> t;
                if(groups[s]==groups[t])
                        cout<<"yes"<<endl;
                else
                        cout<<"no"<<endl;
        }
        return 0;
}

C++: #include<stdio.h>
#include<queue>

using namespace std;

const int MAX = 100000;

int parent(int table[], int child) {
	queue<int> q;

	while (table[child] != -1) {
		q.push(child);
		child = table[child];
	}
	while (!q.empty()) {
		table[q.front()] = child;
		q.pop();
	}
	return child;
}

int main() {
	int n, m, q;
	int table[MAX];

	scanf("%d %d", &n, &m);

	for (int i = 0; i < n; i++)table[i] = -1;
	for (int i = 0; i < m; i++) {
		int s, t;
		scanf("%d %d", &s, &t);
		
		int ps = parent(table, s);
		int pt = parent(table, t);
		if (ps != pt) {
			table[ps] = pt;
		}
	}

	scanf("%d", &q);

	for (int i = 0; i < q; i++) {
		int s, t;
		
		scanf("%d %d", &s, &t);

		int ps = parent(table, s);
		int pt = parent(table, t);

		if (ps == pt) {
			printf("yes\n");
		}
		else {
			printf("no\n");
		}
	}
	return 0;
}

C++: #include<cstdio>
#include<vector>
#define N 100000
using namespace std;

vector<int> G[N];
/*
??£??\??????????????????????????°???????????¨??????????????£????????????????????????DFS??§????????????

 */
int labels[N];

void dfs_init(){
    int i;
    for(i=0;i<N; i++)labels[i]=0;
}

/*
  ?????°?????¨??????????£?
  ??§???????????????????????????
  stack???????????°??§???????????????
 */
bool dfs(int u, int v){
    if (u == v) return true;
    labels[u] = 1;
    int i,x;
    for(i=0; i<G[u].size(); i++){
	x = G[u][i];
	dfs(x,v);
    }
    return false;
}

void dfs2(int u){
    labels[u]=1;
    int i;
    for(i=0; i<G[u].size(); i++){
	if (labels[G[u][i]]==0) dfs2(G[u][i]);
    }
}


int main(void) {
    int n,m,i,q, u,v;
    scanf("%d %d",&n,&m);
    for(i=0;i<m;i++){
	scanf("%d %d",&u,&v);
	G[u].push_back(v);
	G[v].push_back(u);
    }

    
    scanf("%d",&q);
    for(i=0;i<q;i++){
	scanf("%d %d", &u, &v);
	dfs_init();
	dfs2(u);
	if(labels[u]>0 && labels[u]==labels[v])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 <cstdio>
#include <vector>

#define MAX 100000

#define WHITE 0
#define GRAY 1
#define BLACK 2


using namespace std;

vector<int> G[MAX];
int graphc[MAX];
int color[MAX];
int colorCount;

void def(int o)
{
	int v;

	for (int i = 0; i < G[o].size(); i++) {

		v = G[o][i];
		if (color[v] == WHITE) {

			color[v] = GRAY;
			def(v);
		}
	}
	color[o] = BLACK;
	graphc[o] = colorCount;
}


int main(void)
{
	int n;
	int m;
	int s;
	int t;
	int q;


	cin >> n >> m;

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

	for (int i = 0; i < n; i++) {

		if (color[i] == WHITE) {
			colorCount++;
			def(i);
			
		}
	}


	for (int i = 0; i < n; i++) {
		cout << graphc[i] << endl;
	}

	cin >> q;

	for (int i = 0; i < q; i++) {

		cin >> s >> t;

		cout << ((graphc[s] == graphc[t]) ? "yes" : "no" )<< endl;
	}

	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

vector<vector<int>> v;
vector<int> d;

int lx = 1;
void bfs(int x){
  queue<int> q;
  q.push(x);
  d[x] = lx;

  while(!q.empty()){
    int node = q.front();
    q.pop();

    for(int i=0; i<v[node].size(); ++i){
      if(d[v[node][i]] == 0){
         q.push(v[node][i]);
         d[v[node][i]] = lx;
       }
    }
  }
  ++lx;
}

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

  v.resize(n);
  d.resize(n);

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

  for(int i=0; i<n; ++i) if(d[i] == 0) bfs(i);

  int q; cin >> q;
  while(q--){
    int x, y; cin >> x >> y;
    if(d[x] == d[y]) cout << "yes" << endl;
    else cout << "no" << endl;
  }
}