Go: package main

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

//util
var sc = bufio.NewScanner(os.Stdin)

func nextStr() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	n := len(list)
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list[0 : n-1] {
		buf.Write([]byte(fmt.Sprintf("%d ", v)))
	}
	buf.Write([]byte(fmt.Sprintf("%d\n", list[n-1])))
	buf.Flush()
}

func max(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func min(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

//solve
const (
	MAX = 100000
	NIL = -1
)

var (
	n, m, q, s, t int
	G             [MAX][]int //連結リスト
	color         [MAX]int
)

func dfs(r int, c int) {
	S := list.New()
	S.PushFront(r)
	color[r] = c
	for S.Len() != 0 {
		u := S.Remove(S.Front()).(int)
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == NIL {
				color[v] = c
				S.PushFront(v)
			}
		}
	}
}

//幅優先探索で、頂点を色付け
func assignColor() {
	id := 1
	for i := 0; i < n; i++ {
		color[i] = NIL
	}
	for i := 0; i < n; i++ {
		if color[i] == NIL {
			id++
			dfs(i, id)
		}
	}
}

func main() {
	sc.Split(bufio.ScanWords)
	n, m = nextInt(), nextInt()
	for i := 0; i < m; i++ {
		s, t = nextInt(), nextInt()
		if i == 0 {
			G[s] = make([]int, 0)
			G[t] = make([]int, 0)
		}
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)

	}
	assignColor()
	q = nextInt()
	for i := 0; i < q; i++ {
		s, t = nextInt(), nextInt()
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}

}

C++: #include<iostream>
#define MAX 1000001
using namespace std;

int main() {
	int i, n, m, q, a, b, gnum = 0, ptog[MAX] = {};

	cin >> n >> m;
	for (i = 0; i < m; i++) {
		cin >> a >> b;
		if (ptog[a] != 0)ptog[b] = ptog[a];
		else if (ptog[b] != 0)ptog[a] = ptog[b];
		else ptog[a] = ptog[b] = ++gnum;
	}

	cin >> q;
	for (i = 0; i < q; i++) {
		cin >> a >> b;
		if (ptog[a] == ptog[b])cout << "yes\n";
		else cout << "no\n";
	}
}

C++: #include <string>
#include <vector>
#include <stack>
#include <iostream>
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++){
    if(color[s]==color[t]){
      cout <<"yes"<< endl;
    }else{
      cout << "no" <<endl;
    }
  }

  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstring>
#include <stack>
#include <vector>
using namespace std;
const int maxx = 100010;
int n, m;
int u, num, v;
int flag[maxx];
int color[maxx];
vector<int> G[maxx];

int c = 1;
void dfs(int i) {
	stack<int>s;
	s.push(i);
	color[i] = c;
	while (!s.empty()) {
		int u = s.top(); s.pop();
		int len = G[u].size();
		for (int i = 0; i < len; i++) {
			int v = G[u][i];
			if (flag[v] == 0) {
				color[v] = c;
				flag[v] = 1;
				s.push(v);
			}
		}
	}
}
int main()
{
	int q;
	memset(flag, 0, sizeof(flag));
	scanf("%d %d", &n, &m);
	for (int i = 0; i < m; i++) {
		scanf("%d %d", &u, &v);
		//?°???¶???v????????°G[u]??°??????
		G[u].push_back(v);
	}
	for (int i = 0; i < n; i++) {
		if (flag[i] == 0) {
			dfs(i);
			c++;
		}
	}
	scanf("%d", &q);
	for (int i = 0; i < q; i++) {
		scanf("%d %d", &u, &v);
		if (color[u] == color[v]) {
			printf("yes\n");
		}
		else {
			printf("no\n");
		}
	}
	return 0;
}

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

class UnionFind {
	vector<int> data;
	int root(int a) {
		return data[a] < 0 ? a : data[a] = root(data[a]);
	}
public:
	UnionFind(int n) : data(n, -1) {}
	bool Find(int a, int b) {
		return root(a) == root(b);
	}
	void Union(int a, int b) {
		int ra = root(a), rb = root(b);
		if (ra == rb) return;
		if (data[ra] < data[rb]) {
			data[ra] += data[rb];
			data[rb] = a;
		}
		else {
			data[rb] += data[ra];
			data[ra] = b;
		}
	}
};

int main()
{
	int n, m, q;
	cin >> n >> m;
	UnionFind uf(n);
	for (int i = 0, s, t; i < m;i++) {
		cin >> s >> t;
		uf.Union(s, t);
	}
	cin >> q;
	for (int i = 0, s, t; i < q; i++) {
		cin >> s >> t;
		if (uf.Find(s, t))
			cout << "yes" << endl;
		else
			cout << "no" << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <set>
#include <cmath>
#include <deque>
#include <iterator>
#include <map>
#include <queue>
#include <string>
#include <tuple>
#include <utility>
using namespace std;

using ll=long long;
template<class T> using V = vector<T>;
template<class T, class U> using P = pair<T, U>;
using vll = V<ll>;
using vvll = V<vll>;
#define rep(i, k, n) for (ll i=k; i<(ll)n; ++i)
#define REP(i, n) rep(i, 0, n)
template<class T> inline bool chmax(T& a, T b) {if (a<b) {a=b; return true;} return false;}
template<class T> inline bool chmin(T& a, T b) {if (a>b) {a=b; return true;} return false;}

ll n, m;
vvll edges(100000, vll());
vll group(100000, 0);

void dfs(ll i, ll g) {
  if (group.at(i) != 0) return;
  group.at(i) = g;
  REP(j, edges.at(i).size()) {
    if (group.at(edges.at(i).at(j)) == 0) dfs(edges.at(i).at(j), g);
  }
  return;
}

int main() {
  cin >> n >> m;
  REP(i, m) {
    ll a, b; cin >> a >> b;
    edges.at(a).push_back(b); edges.at(b).push_back(a);
  }
  ll g = 1;
  REP(i, n) {
    if (group.at(i) == 0) dfs(i, g++);
  }
  ll q; cin >> q;
  REP(i, q) {
    ll a, b; cin >> a >> b;
    if (group.at(a) == group.at(b)) cout << "yes" << endl;
    else cout << "no" << endl;
  }
  return 0;
}

C++: #include<cstdio>
#include<vector>
#include<algorithm>
#include<utility>
#include<numeric>
#include<iostream>
#include<array>
#include<string>
#include<sstream>
#include<stack>
#include<queue>
#include<list>
#define _USE_MATH_DEFINES

#include<math.h>
#include<map>

#define SENTINEL 1000000001

#define min(a,b) (a)>(b)?(b):(a)
#define max(a,b) (a)>(b)?(a):(b)

using namespace std;

int from[100000];
int to[100000];
bool checked[100000];

bool judge(int f, int t,int n)
{
	if (checked[f])
	{
		return false;
	}

	checked[f] = true;
	bool isFriend = false;
	for (int i = 0; i < n; i++)
	{
		if (from[i] == f)
		{
			if (to[i] == t)
			{
				isFriend = true;
			}
			else
			{
				isFriend = judge(to[i], t, n);
			}
			if (isFriend)
			{
				break;
			}
		}
	}
	return isFriend;
}

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

	for (int i = 0; i < m; i++)
	{
		int f, t;
		cin >> f >> t;

		from[i] = f;
		to[i] = t;
	}

	int q;
	cin >> q;

	for (int i = 0; i < q; i++)
	{
		int f, t;
		cin >> f >> t;

		for (int i = 0; i < n; i++)
		{
			checked[i] = false;
		}

		printf(judge(f, t, n) ? "yes\n" : "no\n");
	}
	return 0;
}