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 <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <queue>
#include <stack>
#include <map>
#define FOR(i,b,e) for(int i=b;i<e;i++)
#define REP(i,n) FOR(i,0,n)
using namespace std;

const int N = 10000;
int n, m, q;
int M[N][N];
bool V[N];

int bfs(int u, int v) {
  int s;
  queue<int> q;
  REP(i, n) V[i] = false;

  s = u;
  q.push(s);
  V[s] = true;

  while (!q.empty() && !V[v]) {
    s = q.front(); q.pop();
    REP(i, n) {
      if (M[s][i] == 1 && !V[i]) {
        q.push(i);
        V[i] = true;
      }
    }
  }

  return V[v];
}

int main() {
	cin.tie(0);
 	ios::sync_with_stdio(false);

  REP(i, n) {
    REP(j, n) {
      M[i][j] = 0;
    }
  }

  cin >> n >> m;
  REP(i, m) {
    int u, v;
    cin >> u >> v;
    M[u][v] = M[v][u] = 1;
  }

  cin >> q;
  REP(i, q) {
    int u, v;
    string answer;
    cin >> u >> v;
    answer = bfs(u, v) ? "yes" : "no";
    cout << answer << endl;
  }
}

C++: 
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<stack>
#include<queue>
#include<vector>
#include<algorithm>
#include<string>
#include<iostream>
using namespace std;

int n,m,q;
static const int N=100005;
vector<int> G[N];
void branch(int a,int b){
    G[a].push_back(b);
    G[b].push_back(a);
}
int color[N];
void dfs(int r,int c){
    stack<int>s;
    s.push(r);
    while(!s.empty()){
        int u=s.top();s.pop();color[u]=c;
        for(int i=0;i<G[u].size();i++){
            if(color[G[u][i]]==0)s.push(G[u][i]);
        }
    }
}
void assigncolor(){
    int id=1;
    for(int u=0;u<n;u++){
        if(color[u]==0){
            dfs(u,id);
            id++;
        }
    }
}
void check(int a,int b){
    if(color[a]==color[b])printf("yes");
    else printf("no");
    printf("\n");
}
int main() {
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        int a,b;cin>>a>>b;
        branch(a,b);
    }
    assigncolor();
    cin>>q;
    for(int i=1;i<=q;i++){
        int a,b;cin>>a>>b;check(a,b);
    }
    return 0;
}

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;
}