Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var (
	n     int
	G     [100000][]int
	color [100000]*int
)

func dfs(r int, c int) {
	S := Stack{}
	S.Push(r)
	color[r] = &c
	for !S.IsEmpty() {
		u := S.Pop()
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == nil {
				color[v] = &c
				S.Push(v)
			}
		}
	}
}

func assignColor() {
	id := 1
	for i := 0; i < n; i++ {
		color[i] = nil
	}
	for u := 0; u < n; u++ {
		if color[u] == nil {
			id++
			dfs(u, id)
		}
	}
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan()
	n, _ = strconv.Atoi(sc.Text())
	sc.Scan()
	r, _ := strconv.Atoi(sc.Text())

	for i := 0; i < r; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	assignColor()
	sc.Scan()
	qNum, _ := strconv.Atoi(sc.Text())
	for i := 0; i < qNum; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

// Stack is Stack
type Stack struct {
	stack []int
}

// Push new value
func (stack *Stack) Push(val int) {
	stack.stack = append(stack.stack, val)
}

// Pop new value
func (stack *Stack) Pop() int {
	val := stack.stack[len(stack.stack)-1]
	stack.stack = stack.stack[0 : len(stack.stack)-1]
	return val
}

// IsEmpty return true when stack is empty
func (stack *Stack) IsEmpty() bool {
	return len(stack.stack) == 0
}

C++: #include<iostream>
#include<vector>
#include<stack>
#include<queue>

struct node {
	int parent;
	std::vector<int> relation;
};

void dfs(std::vector<node> &n) {
	int d[100000];

	std::stack<int> s;
	for (size_t i = 0; i < n.size(); i++) {
		s.push(i);
		for (int k = 0; k < 100000; k++) {
			d[k] = 0;
		}
		while (s.size() != 0) {
			int num = s.top(); s.pop();
			d[num] = 1;
			for (std::vector<int>::iterator it = n[num].relation.begin(); it != n[num].relation.end(); it++) {
				if (d[*it] == 1) {
					n[num].relation.erase(it);
					it--;
				} else {
					s.push(*it);
					d[*it] = 1;
				}
			}
		}
	}
}

void makeparent(std::vector<node> &n) {
	std::queue<int> q;
	for (size_t i = 0; i < n.size(); i++) {
		n[i].parent = -1;
	}
	for (size_t i = 0; i < n.size(); i++) {
		q.push(i);
		int parent = i;
		while (q.size() != 0) {
			parent = q.front(); q.pop();
			for (size_t j = 0; j < n[parent].relation.size(); j++) {
				q.push(n[parent].relation[j]);
				n[n[parent].relation[j]].parent = parent;
			}
		}
	}
}

bool isconnect(std::vector<node> n, int from, int to) {
	std::stack<int> s;
	while (n[from].parent != -1) {
		from = n[from].parent;
	}
	s.push(from);
	while(s.size() != 0) {
		from = s.top(); s.pop();
		for (std::vector<int>::iterator it = n[from].relation.begin(); it != n[from].relation.end(); it++) {
			if (to == *it) return true;
			s.push(*it);
		}
	}
	return false;
}

int main() {
	int people, relation;
	
	std::cin >> people >> relation;

	std::vector<node> n(people);

	for (int i = 0; i < relation; i++) {
		int from, to;
		std::cin >> from >> to;
		n[from].relation.push_back(to);
	}

	dfs(n);
	makeparent(n);

	/*
	for (size_t i = 0; i < n.size(); i++) {
		std::cout << i << " " << n[i].parent << std::endl;
	}
	*/
	int question;
	std::cin >> question;

	for (int i = 0; i < question; i++) {
		int from, to;
		std::cin >> from >> to;
		if (isconnect(n, from, to)) {
			std::cout << "yes" << std::endl;
		} else {
			std::cout << "no" << std::endl;
		}
	}

	return 0;
}

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



int fri[100010];

int find(int x){
  if( fri[x] == x ) return x;
  else return fri[x] = find(fri[x]);
}

bool same(int x, int y){
  return find(x) == find(y);
}

void uf_union(int x, int y){
  x = find(x);
  y = find(y);
  
  fri[x] = y;

}

int main(){

  int n,m,q;
  cin >> n >> m;

  // init
  for(int i=0; i<n; i++) fri[i] = i;

  //
  for(int i=0; i<m; i++){
    int u,v; scanf("%d %d",&u,&v);
    uf_union(u,v);
  }

  cin >> q;
  for(int i=0; i<q; i++){
    int u,v; scanf("%d %d",&u,&v);
    if( find(u) == find(v) ) cout << "yes\n";
    else cout << "no\n";
  }


}

C++: #include<iostream>
#include<climits>
#include<vector>
#include<list>
#include<functional>
#include<algorithm>
#include<string>
#include<cmath>
#include<complex>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<tuple>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) for(int i=0;i<(n);i++)
#define INF (int)1e9
#define INFL (ll)1e11
using namespace std;
typedef long long ll;

typedef pair<int, int> P;

void dfs(int s, int id, vector<vector<int>> a, vector<int> &comp) {
	stack<int> st;
	st.push(s);
	comp[s] = id;
	while (!st.empty()) {
		int i = st.top();
		int k = a[i].size();
		REP(j, k + 1) {
			if (j < k) {
				int t = a[i][j];
				if (comp[t] != id) {
					comp[t] = id;
					st.push(t);
					break;
				}
			}
			else st.pop();
		}
	}
}

void divide(int size, vector<vector<int>> a, vector<int> &comp) {
	int s = 0;
	int id = 1;
	while (1) {
		dfs(s, id, a, comp);
		while (s < size && comp[s]>0) s++;
		if (s == size) break;
		id++;
	}
	return;
}

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

	int n, m;
	cin >> n >> m;
	vector<vector<int>> a(n);
	REP(i, m) {
		int s, t;
		cin >> s >> t;
		a[s].push_back(t);
		a[t].push_back(s);
	}
	int q;
	cin >> q;
	vector<int> comp(n, 0);
	divide(n, a, comp);
	REP(i, q) {
		int s, t;
		cin >> s >> t;
		string res = "no\n";
		if (comp[s] == comp[t]) res = "yes\n";
		cout << res;
	}

	return 0;
}

C++: #include <bits/stdc++.h>
#define REP(i,n) for(int i=0;i<n;++i)

using namespace std;
typedef long long ll;
typedef pair<int,int> P;

vector<set<int>> node;
vector<int> searched;

void solve(int index){
    searched[index]=index;
    queue<int> que; que.push(index);
    while(!que.empty()){
        int order = que.front(); que.pop();
        for(auto itr=node[order].begin();itr!=node[order].end();++itr){
          if(-999==searched[*itr])que.push(*itr);
            searched[*itr]=index;
        }
    }
}

int main(){
   int n,m;cin>>n>>m;
   node.resize(n);
   searched.resize(n,-999); 
   REP(i,m){
    int x,y;cin>>x>>y;
    node[x].insert(y);
    node[y].insert(x);
   }
   REP(i,n)
    if(-999==searched[i])
      solve(i);
   int hm;cin>>hm;
    REP(i,hm){
      int x,y;
      cin>>x>>y;
      if(searched[x]==searched[y]&&searched[y]!=-999&&searched[x]!=-999)
        cout << "yes" << endl;
      else 
        cout << "no" << endl;
    }
}

C++: #define _LIBCPP_DEBUG 0
#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
ll MOD = 1e9 + 7;

vector<int> G[100000+2];
vector<int> visit(100000+2, -1);
int color = 0;

void dfs(int x){

    if(visit[x] > -1)
        return;
    visit[x] = color;

    for (int i = 0; i < G[x].size(); ++i) {
        dfs(G[x][i]);
    }
}


int main(void) {

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

    for (int i = 1; i < n; ++i) {
        if(visit[i]<0){
            color++;
            dfs(i);
        }
    }

    int q; cin>>q;
    for (int i = 0; i < q; ++i) {
        int s,t; cin>>s>>t;
        if(visit[s]==visit[t]) cout<<"yes"<<endl;
        else cout<<"no"<<endl;

    }

    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];
}
if(j!=h){
	d[j]=h;
}
}
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;
}