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 <queue>
#include <cstdio>
using namespace std;
#define MAX_N 1000
int g[MAX_N][MAX_N];
int n;

bool can_connect(int s,int t) {
  bool visited[n];
  queue<int> que;
  visited[s] = true;
  que.push(s);
  while(!que.empty()) {
    int v = que.front(); que.pop();
    for(int i=0;i<n;i++) {
      if(g[v][i] != 0 && !visited[i]) {
        if(i == t) return true;
        visited[i] = true;
        que.push(i);
      }
    }
  }
  return false;
}

int main() {
  int m,s,t,q;
  scanf("%d %d\n",&n,&m);
  for(int i=0;i<m;i++) {
    scanf("%d %d",&s,&t);
    g[s][t] = 1;
    g[t][s] = 1;
  }
  scanf("%d",&q);
  for(int i=0;i<q;i++) {
    scanf("%d %d",&s,&t);
    if(can_connect(s,t)){
      printf("yes\n");
    }
    else {
      printf("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]; // 隣接リスト
int color[MAX]; // グループ(色)を表す配列、同じ色なら同じグループ

// 深さ優先探索
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++) { // id別に連結リスト内を辿る
			int v = G[u][i];
			if (color[v] == NIL) { // まだどのグループにも所属してなければ
				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; // 質問用の友人s,t
	int m, q; // 友人の関係がある数ｍ、質問の個数ｑ

	cin >> n >> m; // 頂点の個数n, 友人関係m

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

	assignColor();

	// 以下、質問パート
	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<algorithm>
#define MAX 100
using namespace std;

int main() {
	int i, n, m, q, a, b, gnum = 0, ptog[MAX] = {};

	cin >> n >> m;
	for (i = 0; i < m; i++) {
		cin >> a >> b;
		if (ptog[a] != 0)ptog[b] = ptog[a];
		else if (ptog[b] != 0)ptog[a] = ptog[b];
		else ptog[a] = ptog[b] = ++gnum;
	}

	cin >> q;
	for (i = 0; i < q; i++) {
		cin >> a >> b;
		if (ptog[a] == ptog[b])cout << "yes\n";
		else cout << "no\n";
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)
#define len(x) ((int)(x).size())
#define mp make_pair
#define eb emplace_back
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;
constexpr int MAX = 1e6;
constexpr int NIL = -1;
int n;
vi G[MAX];
vi color(MAX, NIL);
inline void dfs(int r, int c) {
	deque<int> S;
	S.eb(r);
	color[r] = c;
	int u, v;
	while(!S.empty()) {
		u = S.back(); S.pop_back();
		rep(i, 0, len(G[u])) {
			v = G[u][i];
			if(color[v] == NIL) {
				color[v] = c;
				S.eb(v);
			}
		}
	}
}
inline void assignColor() {
	int id = 0;
	rep(u, 0, n) {
		if(color[u] == NIL) dfs(u, ++id);
	}
}
int main() {
	int m;
	cin >> n >> m;
	int s, t;
	rep(i, 0, m) {
		cin >> s >> t;
		G[s].eb(t);
		G[t].eb(s);
	}
	assignColor();
	int q; cin >> q;
	rep(i, 0, q) {
		cin >> s >> t;
		P(color[s] == color[t] ? "yes" : "no");
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <climits>
#include <cmath>
#include <algorithm>
#include <utility>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#define MAX 100000
#define INFTY 1<<30 // 2^30
using namespace std;
typedef long long llong;
 
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 assingColor()
{
  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);
  }
 
  assingColor();
 
  cin >> q;
  for(int i = 0; i < q; i++)
  {
    cin >> s >> t;
    cout << ((color[s] == color[t]) ? "yes" : "no") << endl;
  }
  return 0;
}

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

using namespace std;

int n, color[10000];
vector<int> G[10000];

void dfs (int r, int c) {

    int i, u, v;

    stack<int> S;
    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] == -1) {
                color[v] = c;
                S.push(v);
            }
        }
    }

}

void assignColor () {

    int id = 1, i, u;

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

}

int main () { 

    int s, t, m, q, 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<stdio.h>
#include<vector>
#include<queue>
#define MAX 100000
using namespace std;
int d[MAX];

int n;
vector <int> M[MAX];


int tail;



void BFS(int s,int t) {
	queue <int>Q;
	Q.push(s);
	d[s] = t;
	while (!Q.empty()) {
		s = Q.front();
		Q.pop();
		for (int j = 0; j < M[s].size(); j++) {
				
				if (d[M[s][j]] == -1) {
					d[M[s][j]] = t;
					Q.push(M[s][j]);
				}
		}

	}
}


int main() {
	int  m, s, t, q;
	scanf("%d %d", &n, &m);

	for (int i = 0; i < m; i++) {
		scanf("%d %d", &s, &t);
		M[s].push_back(t);
		M[t].push_back(s);
	}

	for (int i = 0; i < n; i++) {
		d[i] = -1;
	}
	int count = 0;
	for (int i = 0; i < n; i++) {
		if (d[i] == -1) {
			count++;
			BFS(i, count);
		}
	}
	cin >>q;
	for (int i = 0; i < q; i++) {
		int s2, t2;
		scanf("%d %d", &s2, &t2);
		if (d[s2] == d[t2]) {
			printf("yes\n");
		}
		else {
			printf("no\n");
		}
		
		
	}
	
	return 0;
}