Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	m := getNextInt(scanner)
	nodes := make([]Node, n)

	for i := 0; i < n; i++ {
		nodes[i].list = make([]int, 0)
	}

	for i := 0; i < m; i++ {
		s := getNextInt(scanner)
		t := getNextInt(scanner)
		nodes[s].list = append(nodes[s].list, t)
		nodes[t].list = append(nodes[t].list, s)
	}

	c := 1
	for i := 0; i < n; i++ {
		if nodes[i].c == 0 {
			traverse(nodes, i, c)
			c++
		}
	}

	q := getNextInt(scanner)

	for i := 0; i < q; i++ {
		s := getNextInt(scanner)
		t := getNextInt(scanner)
		if nodes[s].c == nodes[t].c {
			fmt.Fprintln(writer, "yes")
			continue
		}
		fmt.Fprintln(writer, "no")
	}

	writer.Flush()
}

// Node ...
type Node struct {
	list []int
	c    int
}

func traverse(nodes []Node, r, c int) {
	nodes[r].c = c
	for _, i := range nodes[r].list {
		if nodes[i].c != 0 {
			continue
		}
		traverse(nodes, i, c)
	}
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;
int i, j, v, num, color[100000];
vector<int> list[100000];

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] == -1){
       color[v] = c;
       S.push(v);
     }
   }
 }
}
 
void assigncolor(){
 int id = 1;
 for(i=0; i<num; i++){
   color[i] = -1;
 }
 for(i=0; i<num; i++){
   if(color[i] == -1)
     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 rep(i, n) for (int i=0; i<(n); ++i)
using ll = long long;
using P = pair<int, int>;

const int MAX = 100003;
vector<int> G[MAX];
int color[MAX];
int n;

void dfs(int s, int id) {
  stack<int> S;
  S.push(s);
  color[s] = id;

  while (!S.empty()) {
    int u = S.top(); S.pop();
    rep(i,G[u].size()) {
      int v = G[u][i];
      if (color[v] == -1) {
	color[v] = id;
	S.push(v);
      }
    }
  }
}

void assignColor() {
  int id = 1;
  memset(color, -1, sizeof(color));
  rep(u,n) {
    if (color[u] == -1) dfs(u, id++);
  }
}

int main() {
  int m, s, t;
  cin >> n >> m;
  rep(i,m) {
    cin >> s >> t;
    G[s].push_back(t);
    G[t].push_back(s);
  }

  assignColor();

  int q;
  vector<bool> ans;
  cin >> q;
  rep(i,q) {
    cin >> s >> t;
    if (color[s] == color[t]) ans.push_back(true);
    else ans.push_back(false);
  }
  rep(i,q) {
    cout << (ans[i] ? "yes" : "no") << endl;
  }
  return 0;
}

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

int n, m;

bool frend(vector<vector<int>> &M, vector<int> &memo, int i, int t) {
  if (memo[i] == 1) return false;
  for (int z = 0; z < M[i].size(); z++) {
    if (M[i][z] == t) return true;
    memo[i] = 1;
    if (frend(M, memo, M[i][z], t)) { return true; }
  }
  return false;
}

int main() {
  cin >> n >> m;
  vector<vector<int>> M(n);

  for (int i = 0; i < m; i++) {
    int id, f;
    cin >> id >> f;
    M[id].push_back(f);
    M[f].push_back(id);
  }
  int qn;
  cin >> qn;
  vector<vector<int>> q(qn, vector<int>(2));
  for (int i = 0; i < qn; i++) {
    cin >> q[i][0] >> q[i][1];
  }

  for (int i = 0; i < qn; i++) {
    vector<int> memo(n);
    bool res = frend(M, memo, q[i][0], q[i][1]);
    if (res) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }
}

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

using namespace std;

int main(){
	int n, m, s, t, q, i, j;
	int id;
	bool answer_yes = false;

	cin >> n >> m;
	vector< vector<int> > Adj(n);
	vector<int> Stack;
	vector<int> Check(n);
	vector<int>::iterator it, itend;

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

	/*for (i = 0; i < n; i++) {
		cout << "\n" << i << " : " << flush;
		for (auto it2 = Adj[i].begin(); it2 != Adj[i].end(); it2++) {
			cout << *it2 << " " << flush;
		}
	}
	cout << endl;*/

	cin >> q;
	for (i = 0; i < q; i++) {
		cin >> s >> t;
		
		// calculate
		Stack.push_back(s);
		Check[s] = true;
		while (!Stack.empty()) {
			id = Stack.back();
			//cout << "\nid : " << id << " stc : " << Stack.size() << endl;
			itend = Adj[id].end();
			for (it = Adj[id].begin(); it != itend; it++) {
				//cout << *it << " " << flush;
				if (!Check[*it]) {
					if (*it == t) {
						answer_yes = true;
						Stack.clear();
						break;
					}
					Stack.push_back(*it);
					Check[*it] = true;
					break;
				}
			}
			if (it == itend) {
				Stack.pop_back();
			}
		}
		if (answer_yes) {
			cout << "yes" << endl;
		} else {
			cout << "no" << endl;
			Stack.clear();
		}
		answer_yes = false;
		itend = Check.end();
		for (it = Check.begin(); it != itend; it++) {
			*it = false;
		}
	}
	
	return 0;
}

C++: 

#include<iostream>
#include<vector>
#include<stack>

using namespace std;


static const int MAX = 100'000;
static const int nil = -1;

int n;
vector<int> grp[MAX];
int color[MAX];



void dfs(int r, int c) {
	stack<int> stk;
	stk.push(r);
	color[r] = c;

	while (!stk.empty())
	{
		int u = stk.top();stk.pop();

;		for (int i = 0; i < grp[u].size(); i++)
		{
			int v = grp[u][i];
			if (color[v] == nil) {
				color[v] = c;
				stk.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;
		grp[s].push_back(t);
		grp[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;
}