Go: package main

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

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	nNodes := scanInt(sc)
	nConns := scanInt(sc)

	graph := make([][]int, nNodes)
	for i := 0; i < nConns; i++ {
		a, b := scanInt(sc), scanInt(sc)
		graph[a] = append(graph[a], b)
		graph[b] = append(graph[b], a)
	}

	groups := make([]int, nNodes)

	var setGroups func(int, int)
	setGroups = func(u int, groupId int) {
		if groups[u] > 0 {
			return
		}
		groups[u] = groupId

		for _, v := range graph[u] {
			setGroups(v, groupId)
		}
	}
	for i := 0; i < nNodes; i++ {
		setGroups(i, i+1)
	}

	nQuestions := scanInt(sc)

	w := bufio.NewWriter(os.Stdout)
	var ans string
	for i := 0; i < nQuestions; i++ {
		a, b := scanInt(sc), scanInt(sc)
		if groups[a] == groups[b] {
			ans = "yes"
		} else {
			ans = "no"
		}
		fmt.Fprintln(w, ans)
	}
	w.Flush()
}

func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

C++: #include<iostream>
#include<vector>
using namespace std;
void numbering(int v, int k, vector<vector<int>>const&graph, vector<int>&id) {
	
	id[v] = k;
	//v????????????????????????
	//id??????????????°?????????????????????
	//k????????????????????????
	for (auto to : graph[v]) {
		//for(int i=0;i<graph[v].size();++i)
		
		if (id[to] != -1) {
			continue;
		}
		numbering(to, k, graph, id);
	}
}
int main() {
	int n, m;
	cin >> n >> m;
	vector<vector<int>>graph(n);
	for (int i = 0;i < m;++i) {
		int u, v;
		cin >> u >> v;
		graph[u].push_back(v);
		graph[v].push_back(u);
	}
	vector<int>id(n, -1);
	for (int i = 0;i < n;i++) {
		if (id[i] == -1) {
			numbering(i, i, graph, id);
			//numbering(?????????????????????,?????????????????????,graph,id)
		}
	}
	int q;
	cin >> q;
	while (q--) {
		int u, v;
		cin >> u >> v;
		if (id[u] == id[v]) {
			cout <<"yes" << endl;
		}
		else {
			cout << "no" << endl;
		}
	}

}

C++: #include <stdio.h>

int m[100000] = {0};

void init() {
	int i;
	for ( i = 0; i < 100000; ++i) {
		m[i] = i;
	}
}

int find(int n) {
	if ( n == m[n]) {
		return n;
	}
	return m[n] = find(m[n]);
}

int friend (int x, int y) {
	if ( find(x) == find(y)) {
		return 1;
	} else {
		return 0;
	}
}

void unit (int x, int y) {
	x = find(x);
	y = find(y);
	
	if ( x == y ) {
		return ;
	}
	m[y] = x;
}

int main() {
	int n, s, t, u, v, i;
	init();
	scanf("%d", &n);
	scanf("%d", &s);
	
	for ( i = 0; i < s; ++i) {
		scanf("%d", &u);
		scanf("%d", &v);
		unit( u, v);
	}
	
	scanf("%d", &t);
	
	for ( i = 0; i < s; i++) {
		scanf("%d", &u);
		scanf("%d", &v);
		if ( friend( u, v) == 1) {
			printf("yes\n");
		} else {
			printf("no\n");
		}
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#define MAX 100000

using namespace std;

int main(){
  int a[MAX]={};
  int n,m; cin>>n>>m;
  int s,t;
  int group=1;
  for(int i=0;i<m;i++){
    cin>>s>>t;
    if(a[s]==0 && a[t]==0){
      a[s]=a[t]=group;
      group++;
    }else if(a[s]==0){
      a[s]=a[t];
    }else if(a[t]==0){
      a[t]=a[s];
    }else{
      int tmp=a[t];
      a[t]=a[s];
      for(int j=0;j<i;j++){
        if(a[j]==tmp) a[j]=a[s];
      }
    }
  }

  int q; cin>>q;
  for(int i=0;i<q;i++){
    cin>>s>>t;
    if(a[s]==a[t]&&a[s]*a[t]!=0){
      cout<<"yes"<<endl;
    }else{
      cout<<"no"<<endl;
    }
  }

}

C++: #include<iostream>
#include<bits/stdc++.h>
using namespace std;
const int MAX=1e5+9;
int idx[MAX]={0};
void init(){
	int i;
	for(i=0;i<MAX;i++)
		idx[i]=i;
}
int findroot(int i){
	while(i!=idx[i])
		i=idx[i];
	return i;
}
void munion(int u ,int v){
	u=findroot(u);
	v=findroot(v);
	if(u!=v)
		idx[v]=u;
}
int main(){
	int i ,j ,n ,m;
	cin>>n>>m;
	init();
	while(m--){
		int x ,y;
		cin>>x>>y;
		munion(x ,y);
	}
	int q;
	cin>>q;
	while(q--){
		int  u ,v;
		cin>>u>>v;
		u=findroot(u);
		v=findroot(v);
		if(u==v)
			cout<<"Yes"<<"\n";
		else
			cout<<"No"<<"\n";
	}
}

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) {
                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++) {
        cin >> s >> t;
        if (color[s] == color[t]) {
            cout << "yes" << endl;
        } else {
            cout << "no" << endl;
        }
    }
}

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)
            {
                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() 
{
    ios::sync_with_stdio(false);
    
    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(t);
    }

    assignColor();

    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 <stack>
#include <vector>

using namespace std;

const int maxn = 100000;
const int NIL = -1;

vector <int> G[maxn];
int n;
int color[maxn];

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);
    }//邻接表

    assignColor();

    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;
}