Go: package main

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

func main() {
	var n,m int
	fmt.Scan(&n)
	group := make([]int, n)
	for i := 0; i < n; i++ {
		group[i] = i
	}
	
	fmt.Scan(&m)
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	for i := 0; i < m; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())

		if group[s] < group[t] {
			group[t] = group[s]
		} else {
			group[s] = group[t]
		}
	}

	sc.Scan()
	q, _ := strconv.Atoi(sc.Text())
	for i := 0; i < q; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())

		if root(s, &group) == root(t, &group) {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func root(i int, group *[]int) int {
	if i == (*group)[i] {
		return i
	}
	(*group)[i] = root((*group)[i], group)
	return (*group)[i]
}

C++: #include <iostream>
#include <cmath>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
using namespace std;
const int MAXN = 100100 ;
inline int read()
{
	int f = 1, x = 0; char c = getchar();
	while (c < '0' || c > '9') {if (c == '-') f = -1; c = getchar();}
	while (c >= '0' && c <= '9') {x = (x << 3) + (x << 1) + c - '0'; c = getchar();}
	return f * x;
}
int f[MAXN], n, m, q;
int getfa(int x)
{
	if (f[x] == x) return f[x];
	return f[x] = getfa(f[x]);
}
int main()
{
	n = read(); m = read();
	for (int i = 0; i < n; ++i) f[i] = i;
	for (int i = 1, u, v; i <= m; ++i)
	{
		u = read(); v = read();
		int fa1 = getfa(u);
		int fa2 = getfa(v);
		if (fa1 != fa2)
			f[fa1] = fa2;
	}
	q = read();
	for (int i = 1; i <= q; ++i)
	{
		int u, v;
		u = read(); v = read();
		int fa1 = getfa(u), fa2 = getfa(v);
		if (fa1 == fa2) cout << "yes" << endl;
		else cout << "no" << endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int n, m;
vector< list<int> > v;
vector<bool> used;

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

  cin >> n >> m;
  v = vector< list<int> >(n, list<int>(0));
  used = vector<bool>(n, false);
  for(int i = 0; i < m; i++){
    int a, b; cin >> a >> b;
    v[a].push_back(b);
    v[b].push_back(a);
  }
  int q; cin >> q;
  for(int i = 0; i < q; i++){
    used = vector<bool>(n, false);
    int a, b; cin >> a >> b;
    bool flg = false;
    queue<int> que;
    que.push(a);
    while(!que.empty()){
      int q = que.front(); que.pop();
      for(list<int>::iterator it = v[q].begin(); it != v[q].end(); it++){
        if(*it == b){
          flg = true;
          break;
        }
        if(used[*it]) continue;
        used[*it] = true;
        que.push(*it);
      }
      if(flg) break;
    }
    if(flg) cout << "yes" << endl;
    else cout << "no" << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <map>
#include <queue>
using namespace std;
int main(){
  int n,m,t1,t2,c[100000]={}; map <int,bool> g[100000];
  cin>>n>>m;
  for(int i=0;i<m;i++){
    cin>>t1>>t2;g[t1][t2]=1;g[t2][t1]=1;
  }
  int l;cin>>l;
  for(int i=0;i<l;i++){
    queue <int> q;
    bool f[100000]={},find=false;
    cin>>t1>>t2;
    if(c[t1]){
      if(c[t1]==c[t2]) cout<<"yes"<<endl;
      else cout<<"no"<<endl;
      continue;
    }
    q.push(t1);f[t1]=true;c[t1]=i+1;
    for(;!q.empty();){
      for(int j=0;j<n;j++) if(g[q.front()][j]&&!f[j]){
          if(j==t2) find=true;
          f[j]=true;c[t2]=i+1;
          q.push(j);
	}
      q.pop();
      if(find) break;
    }
    if(find) cout<<"yes"<<endl;
    else cout<<"no"<<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <vector>
using namespace std;
#define MAX 100000
#define NIL -1

vector<int> G[MAX];
int c, top, S[MAX], color[MAX];

void dfs_init(int n){
  top = 0;
  for(int i=0; i<n; i++){
    color[i] = NIL;
  }
}

void dfs(int s){
  int v;
  color[s] = c;
  S[++top] = s;
  while(top > 0){
    s = S[top];
    top--;
    for(int i = 0; i<G[s].size(); i++){
      v = G[s][i];
      if(color[v] == NIL){
        S[++top] = v;
        color[v] = c;
      }
    }
  }
}

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

  dfs_init(n);
  for(int i=0; i<n; i++){
    if(color[i] == NIL){
      dfs(i);
      c++;
    }
  }

  c = 0;
  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 = 100000
int i, j, v, num, color[Max];
vector<int> list[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(i=0; i<list[u].size(); i++){
     v = list[u][i];
     if(color[v] == NIL){
       color[v] = c;
       S.push(v);
     }
   }
 }
}
  
void assigncolor(){
 int id = 1;
 for(i=0; i<num; i++){
   color[i] = NIL;
 }
 for(j=0; j<num; j++){
   if(color[j] == NIL)
     dfs(i, id++);
 }
}
  
int main(){
 int a, b, trial, start, goal, kaisuu;
 cin >> num >> kaisuu;
  
 for(i=0; i<kaisuu; i++){
   cin >> a >> b;
   list[a].push_back(b);
   list[b].push_back(a);
 }
 
 assigncolor();
 
 cin >> trial;
 
 for(i=1; i<=trial; i++){
   cin >> start >> goal;
   if(color[start] == color[goal]){  
     cout << "yes" << endl;
   } else{
     cout << "no" << endl;
   }
 }
  
 return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define MAX 100000
#define NIL -1
vector<int>G[MAX];
int color[MAX];
int n;
void dfs(int r,int c){
	color[r]=c;
	stack<int>s;
	s.push(r);
	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(){
	memset(color,-1,sizeof(color));
	int id=1;
	for(int u=0;u<n;u++){
		if(color[u]==NIL)dfs(u,id++);
	}
	 
}


int main(){
	int 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);
	}
	assignColor();
	int q;
	cin>>q;
	for(int i=0;i<q;i++){
		int x,y;
		cin>>x>>y;
		if(color[x]==color[y])cout<<"yes"<<endl;
		else cout<<"no"<<endl;
	}
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;
static const int MAX=10000;
static const int NIL=-1;

int n,color[MAX];
vector<int>G[MAX];

void dfs(int r,int c){
  stack<int> S;
  int u,i,v;
  
  S.push(r);
  color[r]=c;

  
  while(!S.empty()){
    u=S.top();
    S.pop();
    for(i=0;i<G[u].size();i++){
      v=G[u][i];
      if(color[v]==NIL){
	color[v]=c;
	S.push(v);
      }
    }
  }
}

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

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

  assignColor();

  cin>>q;

  for(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>

using namespace std;

vector<int> G[100000], color(100000);
int c;

void dfs(int v) {
	color[v] = c;
	for (int i = 0; i < G[v].size(); ++i) {
		int e = G[v][i];
		if (!color[e]) dfs(e);
	}
}

int main() {
	int n, m; cin >> n >> m;
	while(m--) {
		int s, t; cin >> s >> t;
		G[s].push_back(t);
		G[t].push_back(s);
	}
	for (int i = 0; i < n; ++i) {
		if (!color[i]) {
			c++;
			dfs(i);
		}
	}
	int q; cin >> q;
	while (q--) {
		int s, t; cin >> s >> t;
		if (color[s] == color[t]) cout << "yes" << endl;
		else cout << "no" << endl;
	}

	return 0;
}