Go: package main

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

const (
	MAX = 100000
	NIL = -1
)

var (
	n     int
	G     [MAX][]int
	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)
			}
		}
	}
}

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() {
	var s, t, m, q int
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	scanner.Scan()
	n, _ = strconv.Atoi(scanner.Text())
	scanner.Scan()
	m, _ = strconv.Atoi(scanner.Text())
	for i := 0; i < m; i++ {
		scanner.Scan()
		s, _ = strconv.Atoi(scanner.Text())
		scanner.Scan()
		t, _ = strconv.Atoi(scanner.Text())
		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()
	scanner.Scan()
	q, _ = strconv.Atoi(scanner.Text())
	for i := 0; i < q; i++ {
		scanner.Scan()
		s, _ = strconv.Atoi(scanner.Text())
		scanner.Scan()
		t, _ = strconv.Atoi(scanner.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

C++: #include <bits/stdc++.h>

using namespace std;

typedef long long int ll;
typedef pair<ll, ll> pll;

#define FOR(i, n, m) for(ll (i)=(m);(i)<(n);++(i))
#define REP(i, n) FOR(i,n,0)
#define OF64 std::setprecision(10)

const ll MOD = 1000000007;
const ll INF = (ll) 1e15;

struct Vertex {
    vector<ll> node;
};

Vertex V[100005];
bool U[100005];
ll Parent[100005];

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll N, M;
    cin >> N >> M;
    REP(_, M) {
        ll a, b;
        cin >> a >> b;
        V[a].node.push_back(b);
        V[b].node.push_back(a);
    }

    REP(i, N) {
        Parent[i] = i;
    }
    memset(U, 0, sizeof(U));

    REP(i, N) {
        if (U[i])
            continue;
        queue<ll> q;
        q.push(i);
        U[i] = true;
        while (!q.empty()) {
            ll t = q.front();
            q.pop();
            for (auto &n:V[t].node) {
                if (U[n])
                    continue;
                Parent[n] = i;
                q.push(n);
                U[n] = true;
            }
        }
    }

    ll Q;
    cin >> Q;
    REP(_, Q) {
        ll s, t;
        cin >> s >> t;
        if (Parent[s] == Parent[t])
            cout << "yes" << endl;
        else
            cout << "no" << endl;
    }
    
    return 0;
}

C++: #include <iostream>
#include <math.h>
#include <vector>
#include <algorithm>

using namespace std;
#define MAX 100005
#define NIL -1

vector<int> V[MAX];
int color[MAX];


void search(int v, int c) {
	if (color[v] != NIL)return;
	color[v] = c;
	for (int i = 0; i < V[v].size(); i++) {
		search(V[v][i], c);
	}
}

int main() {
	int n, m;
	cin >> n >> m;
	V->reserve(n);
	for (int i = 0; i < m; i++) {
		int s, t;
		cin >> s >> t;
		V[s].push_back(t);
		V[t].push_back(s);
	}

	int id = 1;
	for (int i = 0; i < n; i++)color[i] = NIL;
	for (int u = 0; u < n; u++) {
		if (color[u] == NIL)search(u, id++);
	}

	int q;
	cin >> q;
	for (int i = 0; i < q; i++) {
		int s, t;
		cin >> s >> t;
		if (color[s] == color[t])cout << "yes\n";
		else cout << "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) {
        S.push(v);
        color[v] = c;
      }
    }
  }
}

void assignColor() {
  int id = 1;
  for (int i = 0; i < n; i++) {
    color[i] = NIL;
  }
  for (int i = 0; i < n; i++) {
    if (color[i] == NIL) {
      dfs(i, id++);
    }
  }
}

int main() {
  int m, u, v, q;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    cin >> u >> v;
    G[u].push_back(v);
    G[v].push_back(u);
  }

  assignColor();

  cin >> q;
  for (int i = 0; i < q; i++) {
    cin >> u >> v;
    if (color[u] == color[v]) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }

  return 0;
}

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

vector<int> list[100000];
int n,m;

bool bfs(int s, int t){
  bool used[m];
  for(int i=0;i<m;i++) used[i]=false; //初期化
  queue<int> Q;
  Q.push(s); used[s]=true;

  while(!Q.empty()){
    int k=Q.front(); Q.pop();
    if(k==t){return true;}
    for(int i=0;i<list[k].size();i++){
      int temp=list[k][i];
      if(!used[temp]){ //未訪問なら
        Q.push(temp); used[temp]=true;
      }
    }
  }
  return false;
}
int main(){
  cin>>n>>m;
  for(int i=0;i<m;i++){
    int u,v; cin>>u>>v;
    list[u].push_back(v);
    list[v].push_back(u);
  }
  int q; cin>>q;
  for(int i=0;i<q;i++){
    int s,t; cin>>s>>t;
    if(bfs(s,t)){
      cout<<"yes"<<"\n";
    }else{
      cout<<"no"<<"\n";
    }
  }
}

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

class person
{
public:
	int id;
	bool Isdone = false;
	list <person*> lis;
	bool serch(person* Per)
	{
		Isdone = true;
		for(list<person*>::iterator temp=lis.begin();temp!=lis.end();++temp)
		{
			if ((*temp) == Per)return true;
			else if ((*temp)->Isdone == true)continue;
			else
			{
				if ((*temp)->serch(Per))return true;
			}
		}
		return false;
	}
};

person P[100001];

int main()
{
	int n, m;
	cin >> n >> m;
	for (int i = 0; i < n; i++)P[i].id = i;
	for (int i = 0; i < m; i++)
	{
		int p1, p2;
		scanf("%d%d",&p1, &p2);
		P[p1].lis.push_back(&P[p2]);
		P[p2].lis.push_back(&P[p1]);
	}			 
	int q;
	cin >> q;
	for (int i = 0; i < q; i++)
	{
		int p1, p2;
		scanf("%d%d", &p1, &p2);
		if (P[p1].serch(&P[p2]))
		{
			cout << "yes" << endl;
		}
		else
		{
			cout << "no" << endl;
		}
		for (int l = 0; l < n; l++)P[l].Isdone = false;
	}
	return 0;
}

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

int n;
vector<int> G[100005];
vector<int> color(100005, -1);
vector<bool> seen(100005, false);

void dfs(int now, int id){
    seen[now] = true;
    color[now] = id;

    for(int i=0; i<G[now].size(); ++i){
        int to = G[now][i];
        if(!seen[to]) dfs(to, id);
    }
}

int main(){
    
    int m; cin >> n >> m;
    for(int i=0; i<m; ++i){
        int a,b; cin >> a >> b;
        G[a].push_back(b);
        G[b].push_back(a);
    }

    int id = 0;
    for(int i=0; i<n; ++i){
        if(!seen[i]){
            ++id;
            dfs(i, id);
        }
    }

    int q; cin >> q;
    for(int i=0; i<q; ++i){
        int s, t; cin >> s >> t;
        if(color[s] == color[t]) printf("yes\n");
        else printf("no\n");
    }

    return 0;
}