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 <stdio.h>
#include <iostream>
#include <queue>
using namespace std;

#define NODE_NUM 100000

queue<int> que;

class Node
{
private:
	int next_num;
	int next_node_list[NODE_NUM];
public:
	Node();
	void AddNextNode(int id);
	bool Search(int st, int ed);
	bool check[NODE_NUM];
	bool link[NODE_NUM];
};

Node::Node()
{
	next_num = 0;
	for (int i = 0; i < NODE_NUM; i++) {
		check[i] = false;
	}
	for (int i = 0; i < NODE_NUM; i++) {
		link[i] = false;
	}
}

void Node::AddNextNode(int id)
{
	next_node_list[next_num] = id;
	next_num++;
}

Node *Node_list;

bool Node::Search(int st, int ed)
{
	if (link[ed]) return true;

	for (int k = 0; k < next_num; k++) {
		Node_list[st].link[next_node_list[k]] = true;
	}

	for (int i = 0; i < next_num; i++) {
		if (next_node_list[i] == ed) return true;
	}
	
	for (int j = 0; j < next_num; j++) {
		if (Node_list[next_node_list[j]].check[ed] == 0) {
			Node_list[next_node_list[j]].check[ed] = 1;
			que.push(next_node_list[j]);
		}
	}
	
	return false;
}

int main(void)
{
	//input
	int n;
	cin >> n;
	Node_list = new Node[n]();
	int m;
	cin >> m;
	for (int i = 0; i < m; i++) {
		int s, t;
		cin >> s >> t;
		Node_list[s].AddNextNode(t);
		Node_list[t].AddNextNode(s);
	}
	
	//output
	int q;
	cin >> q;
	for (int i = 0; i < q; i++) {
		int s, t;
		cin >> s >> t;
		bool ret = Node_list[s].Search(s, t);
		while (!ret && !que.empty()) {
			ret = Node_list[que.front()].Search(s, t);
			que.pop();
		};
		while (!que.empty()) {
			que.pop();
		}

		if (ret) {
			cout << "yes" << "\n";
		}
		else {
			cout << "no" << "\n";
		}
	}
	
	return 0;
}

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

using namespace std;

class UnionFind
{
public:
	vector<int> par;
	vector<int> rk;
	UnionFind(int n)
	{
		par.resize(n);
		rk.resize(n);
		for (int i = 0; i < n; ++i)
		{
			par[i] = i;
		}
	}
	int find(int x)
	{
		if (par[x] == x)
		{
			return(x);
		}
		return(par[x] = find(par[x]));
	}
	void unite(int x, int y)
	{
		x = find(x);
		y = find(y);
		if (rk[x] < rk[y])
		{
			par[x] = y;
		}
		else
		{
			par[y] = x;
			if (rk[x] == rk[y])
			{
				++rk[x];
			}
		}
	}
	bool same(int x, int y)
	{
		return(find(x) == find(y));
	}
};


void solve()
{
	int n, m;
	cin >> n >> m;
	UnionFind uf(n);
	for (int i = 0; i < m; ++i)
	{
		int s, t;
		cin >> s >> t;
		uf.unite(s, t);
	}
	int q;
	cin >> q;
	for (int i = 0; i < q; ++i)
	{
		int s, t;
		cin >> s >> t;
		if (uf.same(s, t))
		{
			cout << "yes" << endl;
		}
		else
		{
			cout << "no" << endl;
		}
	}
}

int main()
{
	solve();
	return(0);
}

C++: #include <stdio.h>
#include <iostream>
using namespace std;

class Node{
private:
	int id;
	int friend_num;
	Node **friends;
	int check_id;
public:
	Node(int id, int n);
	~Node(){ delete[] friends; }
	void addFriend(Node *friend_node);
	bool searchFriend(int id);
};

Node::Node(int id, int n)
{
	this->id = id;
	friend_num = 0;
	friends = new Node*[n];
	check_id = -1;
}

void Node::addFriend(Node *friend_node)
{
	friends[friend_num] = friend_node;
	friend_num++;
}

bool Node::searchFriend(int id)
{
	if (check_id == id) return false;
	check_id = id;

	if (this->id == id) {
		check_id = -1;
		return true;
	}

	for (int i = 0; i < friend_num; i++) {
		if (friends[i]->searchFriend(id)) {
			check_id = -1;
			return true;
		}
	}
	check_id = -1;
	return false;
}

int main(void)
{
	int n;
	cin >> n;	
	Node **node = new Node*[n];
	for (int i = 0; i < n; i++) node[i] = new Node(i, n);

	int m;
	cin >> m;
	for (int i = 0; i < m; i++) {
		int s, t;
		cin >> s >> t;
		node[s]->addFriend(node[t]);
		node[t]->addFriend(node[s]);
	}
		
	int q;
	cin >> q;
	for (int i = 0; i < q; i++) {
		int s, t;
		cin >> s >> t;
		bool result = node[s]->searchFriend(t);
		if (result) cout << "yes" << endl;
		else cout << "no" << endl;
	}

	delete[] node;
	return 0;
}

C++: #include<iostream>
#include<cstring>
using namespace std;

bool x[10000][10000];
bool y[10000];

int main(){
	int n,m,a,b,q;
	cin>>n>>m;
	for(int i=0;i<m;i++){
		cin>>a>>b;
		x[a][b]=true;
		x[b][a]=true;
	}
	cin>>q;
	for(int h=0;h<q;h++){
		cin>>a>>b;
		memset(y,0,sizeof(y));
		y[a]=true;
		for(int i=0;i<50;i++){
			for(int j=0;j<n;j++){
				if(y[j]==true){
					for(int k=0;k<n;k++){
						if(x[j][k]==true){
							y[k]=true;
						}
					}
				}
				if(y[b]==true){
					cout<<"yes"<<endl;
					goto Exit;
				}
			}
		}
		cout<<"no"<<endl;
		Exit:;
	}
	return 0;
}

C++: #include <stdio.h>
#include <stack>
#include <vector> 
#include <iostream>
#define N 100000
using namespace std;

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

void dfs(int s, int c)
{
    stack<int> st;
    color[s] = c;
    st.push(s);
    while(!st.empty())
    {
        int u = st.top();
        st.pop();
        for (int i = 0; i < G[u].size(); i++)
        {
            int v = G[u][i];
            if(color[v] == -1)
            {
                color[v] = c;
                st.push(v);
            }
        } 
    }
    return;
}

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

    return;
}

int main()
{
    //freopen("in3.txt","r",stdin);
    int m;
    scanf("%d %d",&n, &m);

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

    assignColor(); 

    int q,s,t;
    scanf("%d",&q);
    for (int i = 0; i < q; i++)
    {
        scanf("%d %d",&s,&t);
        if (color[s] == color[t])
        { 
            printf("yes\n"); 
        } else
        { 
            printf("no\n"); 
        } 
    } 
    return 0;
}