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<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;
		}
	}

	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>

#define MAX 100000

#define WHITE 0
#define GRAY 1
#define BLACK 2


using namespace std;

vector<int> G[MAX];
int graphc[MAX];
int color[MAX];
int colorCount;

void def(int o)
{
	int v;

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

		v = G[o][i];
		if (color[v] == WHITE) {

			color[v] = GRAY;
			def(v);
		}
	}
	color[o] = BLACK;
	graphc[o] = colorCount;
}


int main(void)
{
	int n;
	int m;
	int s;
	int t;
	int q;


	cin >> n >> m;

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

	for (int i = 0; i < n; i++) {

		if (color[i] == WHITE) {
			colorCount++;
			def(i);
			
		}
	}


	for (int i = 0; i < n; i++) {
		cout << graphc[i] << endl;
	}

	cin >> q;

	for (int i = 0; i < q; i++) {

		cin >> s >> t;

		cout << ((graphc[s] == graphc[t]) ? "yes" : "no" )<< endl;
	}

	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

vector<vector<int>> v;
vector<int> d;

int lx = 1;
void bfs(int x){
  queue<int> q;
  q.push(x);
  d[x] = lx;

  while(!q.empty()){
    int node = q.front();
    q.pop();

    for(int i=0; i<v[node].size(); ++i){
      if(d[v[node][i]] == 0){
         q.push(v[node][i]);
         d[v[node][i]] = lx;
       }
    }
  }
  ++lx;
}

int main(){
  int n, m; cin >> n >> m;

  v.resize(n);
  d.resize(n);

  for(int i=0; i<m; ++i){
    int x, y; cin >> x >> y;
    v[x].push_back(y);
    v[y].push_back(x);
  }

  for(int i=0; i<n; ++i) if(d[i] == 0) bfs(i);

  int q; cin >> q;
  while(q--){
    int x, y; cin >> x >> y;
    if(d[x] == d[y]) cout << "yes" << endl;
    else cout << "no" << endl;
  }
}

C++: #include <cstdio>
#include <vector>
#include <cstring>
#include <cstdlib>

void numbering(int id, int *g, int num, std::vector<int> *a){
    int tmp;
    for(int i=0;i<a[id].size();i++){
        tmp = a[id][i];
        if(g[tmp])continue;
        g[tmp] = num;
        numbering(tmp, g, num, a);
    }
}

void grouping(std::vector<int> *a, int *g, int n){
    int num = 1;
    for(int i=0;i<n;i++){
        if(g[i])continue;
        g[num] = num;
        numbering(i,g,num,a);
        num++;
    }
}

int main(){
    int i, n, m, q, s, t;
    int *g;
    scanf("%d %d",&n,&m);
    g = (int *)malloc(sizeof(int)*n);
    memset(g, 0, sizeof(int)*n);
    std::vector<int> a[n];
    for(i=0;i<m;i++){
        scanf("%d %d",&s,&t);
        a[s].push_back(t);
        a[t].push_back(s);
    }
    scanf("%d",&q);
    grouping(a,g,n);
    for(i=0;i<q;i++){
        scanf("%d %d",&s,&t);
        if(g[s]==g[t])printf("yes\n");
        else printf("no\n");
    }
    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define rep(i,N) for(ll i=0;i<N;++i)
typedef long long int ll;
ll INF = 1LL<<60;

ll n,m;

struct UnionFind {
  vector< int > data;
 
  UnionFind(int sz) {
    data.assign(sz, -1);
  }
 
  bool unite(int x, int y) {
    x = find(x), y = find(y);
    if(x == y) return (false);
    if(data[x] > data[y]) swap(x, y);
    data[x] += data[y];
    data[y] = x;
    return (true);
  }
 
  int find(int k) {
    if(data[k] < 0) return (k);
    return (data[k] = find(data[k]));
  }
 
  int size(int k) {
    return (-data[find(k)]);
  }
};

int main(){
    cin >> n >> m;
    UnionFind tree(n);
    rep(i,m){
        int x,y; cin >> x >> y;
        tree.unite(x,y);
    }
    int q; cin >> q;
    rep(i,q){
        int x,y; cin >> x >> y;
        if(tree.find(x) != -1 && tree.find(y) != -1){
            if(tree.find(x) == tree.find(y)) cout << "yes" << endl;
            else cout << "no" << endl;
        }else cout << "no" << endl;
    }
}