Go: package main

import (
	"fmt"
)

var n, m int
var g [][]int
var color []int

func main() {
	fmt.Scan(&n, &m)
	g = make([][]int, n) // SNSの関係を表すグラフ
	for i := 0; i < m; i++ {
		var a, b int
		fmt.Scan(&a, &b)
		g[a] = append(g[a], b) // 無向重みなしグラフ
		g[b] = append(g[b], a)
	}
	color = make([]int, n) // 各ノードにつける色
	for i := 0; i < len(color); i++ {
		color[i] = -1 // 初期化しておく
	}
	type query struct {
		s, t int
	}
	var Q int
	fmt.Scan(&Q)
	qs := make([]query, Q)
	for i := 0; i < Q; i++ {
		fmt.Scan(&qs[i].s, &qs[i].t)
	}
	// fmt.Println("n", n, "m", m, "g", g, "Q", Q, "qs", qs)
	// 全ての頂点からdfsする
	id := 1
	for u := 0; u < n; u++ {
		if color[u] == -1 {
			dfs(u, id)
			id++
		}
	}
	// fmt.Println("color", color)
	for i := 0; i < Q; i++ {
		if color[qs[i].s] == color[qs[i].t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func dfs(v, c int) {
	// fmt.Printf("dfs(v %d, c %d) en:\n", v, c)
	color[v] = c
	for _, vv := range g[v] {
		// fmt.Printf("  v %d, g[v] %v, vv %d\n", v, g[v], vv)
		if color[vv] == -1 {
			dfs(vv, c)
		}
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i, n) for (ll i = 0; i < (ll)n; ++i)
ll dx[4] = { 0, 1, 0, -1 };
ll dy[4] = { 1, 0, -1, 0 };
const ll INF = 1 << 21;
const ll MOD = 1e9 + 7;

static const int N = 1e5;
static const int NIL = -1;

int n, m, q;
vector<int> G[N];
int color[N];

void dfs(int r, int c)
{
    stack<int> S;
    S.push(r);
    color[r] = c;
    while(!S.empty()) {
        int u = S.top();
        S.pop();
        rep(i, G[u].size()) {
            int v = G[u][i];
            if (color[v] == NIL) {
                color[v] = c;
                S.push(v);
            }
        }
    }
}

void assigncolor()
{
    int id = 1; // 同じidがcolorに格納されているときは同じ連結成分にある
    // 初期化
    rep(i, n) {
        color[i] = NIL;
    }
    rep(u, n) {
        if (color[u] == NIL) { // 初期化されていた場合
            dfs(u, id++);
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    rep(i, m)
    {
        int s, t;
        cin >> s >> t;
        G[s].push_back(t);
        G[t].push_back(s);
    }

    assigncolor();

    cin >> q;
    rep(i, q)
    {
        int s, t;
        cin >> s >> t;
        if (color[s] == color[t]) {
            puts("yes");
        } else {
            puts("no");
        }
    }
    return 0;
}

C++: //
//  main.cpp
//  connected_components
//
//  Created by ???????????? on 2017/10/22.
//  Copyright ?? 2017 ????????????. All rights reserved.
//

#include <iostream>
#include <stdio.h>
#include <vector>

using namespace std;

#define n_max 100000
//#define vector_max 100000
#define WHITE 0
#define GRAY 1
#define BLACK 2

bool found;
int n, target, t = 0;
int color[n_max], d[n_max], f[n_max];
vector<int> G[n_max];

void encode_graph_list(){
    int i, id, node, f;
    
    scanf("%d", &n);
    scanf("%d", &node);
    
    for (i = 0; i < node; i++){
        scanf("%d", &id);
        scanf("%d", &f);
        G[id].push_back(f);
    }
    
}

void dfs(int u){
//    found = false;
//    if(target == u) {
//        found = true;
//        return;
//    }
    color[u] = GRAY;
    d[u] = ++t;
    for (int v = 0; v < G[u].size(); v++){
        int t = G[u][v];
        if(color[t] == WHITE){
            dfs(t);
        }
    }
    color[u] = BLACK;
    f[u] = ++t;
}

void dfs_init(int start){
    for(int i = 0; i < n ; i++){
        color[i] = WHITE;
    }
    dfs(start);
}



int main(int argc, const char * argv[]) {
    int qs, i, id;
    encode_graph_list();
    scanf("%d", &qs);
    dfs_init(0);
    for (i = 0; i < qs; i++){
        scanf("%d %d", &id, &target);
        if(color[target] == color[id]) cout << "yes" <<endl;
        else cout << "no"<<endl;
    }
//    std::cout << "Hello, World!\n";
    return 0;
}

C++: #include <iostream>
using namespace std;
 
int main() {
int d[100100];
int m,n,q;
cin>>n>>m;
for(int i=0;i<n;i++){
    d[i]=i;
}
for(int l=0;l<m;l++){
    int a,b;
    cin>>a>>b;
    int j ,h;
    j=a,h=b;
while(d[j]!=j ||d[h]!=h){
    j=d[j];
    h=d[h];
}
d[j]=h;
while(a!=h){
 
    d[a]=h;
    d[b]=h;
a=d[a];
b=d[b];
}
}

cin>>q;
for(int y=0;y<q;y++){
    int a,b;
    cin>>a>>b;
        int j ,h;
    j=a,h=b;
while(d[j]!=j ||d[h]!=h){
    j=d[j];
    h=d[h];
}
    if(j==h){
        cout<<"yes"<<endl;
    }
    else{
        cout<<"no"<<endl;
    }
}
    return 0;
}

C++: #define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<cstdio>
#include<string>
#include<algorithm>
#include<cmath>
#include<vector>
#include<stack>
using namespace std;

#define REP(i,n) for(int i=0;(i)<(n);(i)++)

vector<int> adjacencyList[100005];//??£??\?????????

int n;
int color[100005];//????????????????????°?????????????±???????????????????


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 < adjacencyList[u].size();i++) {
			int v = adjacencyList[u][i];
			if (color[v] == -1) {
				color[v] = c;
				S.push(v);
			}
		}
	}
}

void assignColor() {
	REP(i, n) color[i] = -1; //?????????

	//?????????
	int next_color = 1;
	REP(i, n) {
		if (color[i] == -1) {
			dfs(i, next_color++);
		}
	}
}


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

	int s, t;
	REP(i, m) {
		cin >> s >> t;
		adjacencyList[s].push_back(t);
		adjacencyList[t].push_back(s);
	}

	assignColor();//?????????

	int q;
	cin >> q;
	REP(i, q) {
		cin >> s >> t;//s??????t?????????????????¨???????????¨???

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

	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<queue>
#include<utility>
#include<vector>

using namespace std;



int main() {
	int cnt_people, cnt_relation;
	queue<int> q;
	int cnt_equiv = 0;
	cin >> cnt_people >> cnt_relation;

	vector<int> *adjacent=new vector<int>[cnt_people];
	int* equiv = new int[cnt_people];
	for (int i = 0;i < cnt_people;i++) {
		equiv[i] = -1;
	}
	int tmp1, tmp2;
	for (int i = 0;i < cnt_relation;i++) {
		cin >> tmp1>>tmp2;
		adjacent[tmp1].push_back(tmp2);
		adjacent[tmp2].push_back(tmp1);
	}
	for (int i = 0;i < cnt_people;i++) {
		if (equiv[i] == -1) {
			cnt_equiv++;
			equiv[i] = cnt_equiv;
			q.push(i);
			while (!q.empty()) {
				tmp1 = q.front();
				q.pop();
				for (int j = 0;j < adjacent[tmp1].size();j++) {
					if (equiv[adjacent[tmp1][j]] == -1) {
						equiv[adjacent[tmp1][j]] = cnt_equiv;
						q.push(adjacent[tmp1][j]);
					}
				}
			}
		}
	}
	int cnt_question;
	cin >> cnt_question;
	for (int i = 0;i < cnt_question;i++) {
		cin >> tmp1 >> tmp2;
		if (equiv[tmp1] == equiv[tmp2]) {
			cout << "yes\n";
		}
		else {
			cout << "no\n";
		}
	}
}

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;
}