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>
#include <vector>
#include <algorithm>
using namespace std;
vector<int> flags;
typedef class unionfindtree{
private:
	std::vector<int> par,rank;
public:
	void init(int n){
		for(int i=0;i<n;i++){
			par.push_back(i);
			rank.push_back(0);
		}
	}
	int find(int x){
		if(par[x]==x) return x;
		return par[x]=find(par[x]);
	}
	bool same(int x,int y){
		if(find(x)==find(y)) return true;
		else return false;
	}
	void uni(int x,int y){
		x=find(x);
		y=find(y);
		if(rank[x]>=rank[y]){
			par[y]=x;
			rank[x]=rank[x]+1;
		}else if(rank[x]<rank[y]){
			par[x]=y;
			rank[y]=rank[y]+1;
		}
	}
}UFT;
struct input_data{
	int id1;
	int id2;
	bool operator<(const input_data& rhs)const{
		if(min(id1,id2)<min(rhs.id1,rhs.id2)) return true;
		if(min(id1,id2)==min(rhs.id1,rhs.id2) && max(id1,id2)<max(rhs.id1,rhs.id2)) return true;
		return false;
	}
};
vector<input_data> d;
UFT uft;
void input(int m){
  for(int i=0;i<m;i++){
    int id1,id2;
    cin>>id1>>id2;
  	input_data ind={id1,id2};
  	d.push_back(ind);
  }
	stable_sort(d.begin(),d.end());
}

void reuni(int n){
	for(input_data ind:d){
		if(!uft.same(ind.id1,ind.id2)){
			uft.uni(ind.id1,ind.id2);
		}
	}
}

void cc(int q){
  for(int i=0;i<q;i++){
	  int id1,id2;
  		cin>>id1>>id2;
  		if(uft.same(id1,id2)) flags.push_back(1);
  	else flags.push_back(0);
  }
}
int main(){
  int n,m;
  cin>>n>>m;
  input(m);
	uft.init(n);
	reuni(n);
	int q;
	cin>>q;
	cc(q);
	for(int f:flags){
		if(f) cout<<"yes"<<endl;
		else cout<<"no"<<endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
vector<int> G[100000];
int group[100000]={0};

void dfs(int v,int g){
	group[v] = g;
	for(int i=0;i<G[v].size();i++)
		if(!group[G[v][i]]) 
			dfs(G[v][i],g);
}

int main()
{	
	int n,m,u,v;
	cin>>n>>m;
	while(m--){
		scanf("%d%d",&u,&v);
		G[u].push_back(v);
		G[v].push_back(u);
	}
	int g = 1;
	for(int i=0;i<n;i++)
		if(!group[i]) dfs(i,g++);
	cin>>m;
	while(m--){
		scanf("%d%d",&u,&v);
		if(group[u]==group[v])
			puts("yes");
		else puts("no");
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;
static const int Max = 100000;
static const int NIL = -1;
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 <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 t) {
	stack<int>s;
	s.push(t);
	color[t] = 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);
		G[v].push_back(u);
	}
	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 <iostream>
#include <vector>
#include<stack>
using namespace std;
static const int MAX = 10000;
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 assign(){
	int id=1;
	for(int i=0;i<n;i++){
		color[i] = NIL;
	}
	for(int j=0;j<n;j++){
		if(color[j]==NIL){
			dfs(j,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);
	}
	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;
}