Go: package main

import (
	"fmt"
	"os"
	"bufio"
	"strconv"
	"container/list"
	"bytes"
)

const MaxNode int = 1e5

var graph [][] int
var color []int
var N int

func bfs(u, c int) {
	l := list.New()
	l.PushBack(u)
	for ;l.Len()!=0; {
		u = l.Front().Value.(int)
		color[u] = c
		l.Remove(l.Front())
		for i:=0; i<len(graph[u]); i++ {
			if color[graph[u][i]] == 0 {
				l.PushBack(graph[u][i])
			}
		}
	}
}

func assignColor() {
	id := 1
	for u:=0; u<N; u++ {
		if color[u] == 0 {
			bfs(u, id)
			id ++
		}
	}
}

func nextInt(scanner *bufio.Scanner) int {
	scanner.Scan()
	num, _ := strconv.Atoi(scanner.Text())
	return num
}


func buildGraph(scanner *bufio.Scanner) {
	N = nextInt(scanner)
	color = make([]int, N)
	graph = make([][]int, N)
	m := nextInt(scanner)
	for i:=0; i<m; i++ {
		n1 := nextInt(scanner)
		n2 := nextInt(scanner)
		graph[n1] = append(graph[n1], n2)
		graph[n2] = append(graph[n2], n1)
	}
}

func answer(scanner *bufio.Scanner) {
	var outBuffer bytes.Buffer
	cnt := nextInt(scanner)
	for i:=0; i<cnt; i++ {
		n1 := nextInt(scanner)
		n2 := nextInt(scanner)
		if color[n1] == color[n2] {
			outBuffer.WriteString("yes\n")
		} else {
			outBuffer.WriteString("no\n")
		}
	}
	fmt.Printf("%s", outBuffer.String())
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	buildGraph(scanner)
	assignColor()
	answer(scanner)
}

C++: // http://hfuji.hatenablog.jp/entry/2015/12/09/175721

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cassert>
#include <string>
#include <cstring>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>

using namespace std;

// ---------------------
// repetition
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)

// debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

// ---------------------
#define INF 922337203685477580
typedef long long ll;
vector<int> par;
vector<int> rnk; // ??±???

void init(int n) {
  par = vector<int>(n);
  rnk = vector<int>(n);
  REP(i, n) {
    par[i] = i;
    rnk[i] = 0;
  }
}
int root(int key) {
  if (par[key] == key) return key;
  return root(par[key]);
}
int same(int a, int b) {
  return root(a) == root(b);
}
void unite(int a, int b) {
  int x = root(a);
  int y = root(b);
  if (x == y) return;

  if (rnk[x] < rnk[y]) {
    par[x] = y;
  } else {
    par[y] = x;
    if (rnk[x] == rnk[y]) rnk[x]++;
  }
}

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

  init(n);

  REP(_, m) {
    int a, b;
    // cin >> a >> b;
    scanf("%d %d", &a, &b);
    unite(a, b);
  }
  int q;
  cin >> q;
  REP(_, q) {
    int a, b;
    // cin >> a >> b;
    scanf("%d %d", &a, &b);
    if (same(a, b)) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }

  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define MAX 1001001
#define NIL -1

/*
  疎なグラフ(連結成分が少ないグラフ)では、隣接行列を使うのはメモリefficientではない。
  ->隣接リストを用いて各ノードの関係を表す

  連結成分を求めるには、未訪問のノードを始点としてDFSを行う。
  この探索を行うごとに、各点に異なるIDを割り振ることで、どのグループに属するかを判定する。
*/

int n;
vector<int> G[MAX]; //頂点数がMAXまで格納できる隣接リスト(中身は配列)
int color[MAX]; //

void dfs_colorAssign(int start, int group_id) {
  stack<int> s;
  s.push(start);
  color[start] = group_id;

  while(!s.empty()) {
    int now = s.top(); s.pop();

    for (int i = 0; i < G[now].size(); i++) {
      int v = G[now][i];
      if (color[v] == NIL) {
        color[v] = group_id;
        s.push(v);
      }
    }
  }
}

void assign_color() {
  int id = 1;
  for (int i = 0; i < n; i++) color[i] = NIL; //color配列を初期化
  //未訪問の頂点はidがNILになる
  for (int i = 0; i < n; i++) {
    if (color[i] == NIL) dfs_colorAssign(i, id);
    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); // 互いの隣接リストに相手を追加
    G[t].push_back(s);
  }

  assign_color();

  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<vector>
#include<stack>
using namespace std;
static const int NIL = -1;
static const int MAX = 100000;

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 <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(void){
    int s,t,m,q;
    scanf("%d %d",&n,&m);
    for(int i=0;i<m;i++){
        scanf("%d %d",&s,&t);
        G[s].push_back(t);
        G[t].push_back(s);
    }
    assignColor();
    scanf("%d",&q);
    for(int i=0;i<q;i++){
        scanf("%d %d",&s,&t);
        if(color[s] == color[t])
            puts("yes");
        else
            puts("no");
    }
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
vector<int> flags;
typedef class unionfindtree{
private:
	std::vector<int> par,rank;
public:
	void init(int n){
		for(int i=0;i<n;i++){
			par.push_back(i);
			rank.push_back(0);
		}
	}
	int find(int x){
		if(par[x]==x) return x;
		return par[x]=find(par[x]);
	}
	bool same(int x,int y){
		if(find(x)==find(y)) return true;
		else return false;
	}
	void uni(int x,int y){
		x=find(x);
		y=find(y);
		if(rank[x]>=rank[y]){
			par[y]=x;
			rank[x]=rank[x]+1;
		}else if(rank[x]<rank[y]){
			par[x]=y;
			rank[y]=rank[y]+1;
		}
	}
}UFT;
struct input_data{
	int id1;
	int id2;
	bool operator<(const input_data& rhs)const{
		if(min(id1,id2)<min(rhs.id1,rhs.id2)) return true;
		if(min(id1,id2)==min(rhs.id1,rhs.id2) && max(id1,id2)<max(rhs.id1,rhs.id2)) return true;
		return false;
	}
};
vector<input_data> d;
UFT uft;
void input(int m){
  for(int i=0;i<m;i++){
    int id1,id2;
    cin>>id1>>id2;
  	input_data ind={id1,id2};
  	d.push_back(ind);
  }
	stable_sort(d.begin(),d.end());
}

void reuni(int n){
	for(input_data ind:d){
		if(!uft.same(ind.id1,ind.id2)){
			uft.uni(ind.id1,ind.id2);
		}
	}
}

void cc(int q){
  for(int i=0;i<q;i++){
	  int id1,id2;
  		cin>>id1>>id2;
  		if(uft.same(id1,id2)) flags.push_back(1);
  	else flags.push_back(0);
  }
}
int main(){
  int n,m;
  cin>>n>>m;
  input(m);
	uft.init(n);
	reuni(n);
	int q;
	cin>>q;
	cc(q);
	for(int f:flags){
		if(f) cout<<"yes"<<endl;
		else cout<<"no"<<endl;
	}
	return 0;
}