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>
#include<stack>
using namespace std;

bool DFS(const vector<vector<int> >& G, int a, int b) {
    if (G[a].size() == 0) return false;

    stack<pair<int, int> > S;
    vector<bool> is_visited(G.size(), false);

    int idx = 0;
    do {
        if (idx >= G[a].size()) {
            a   = S.top().first;
            idx = S.top().second;
            S.pop();
            idx++;
            continue;
        }
        if (G[a][idx] == b) return true;
        if (!is_visited[G[a][idx]]) {
            is_visited[G[a][idx]] = true;
            S.push(make_pair(a, idx));
            a   = G[a][idx];
            idx = 0;
            continue;
        }
        idx++;
    } while (!S.empty());
    return false;
}


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

vector<vector<bool> > D(100000, vector<bool>(100000));

    vector<vector<int> > G(n);

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

// for (int i = 0; i < n; i++) {
//     cout << i << " : ";
//     for (int j = 0; j < G[i].size(); j++){
//         cout << G[i][j] << " ";
//     }
//     cout << endl;
// }



    int q;
    cin >> q;
    for (int i = 0; i < q; i++) {
        int a, b;
        cin >> a >> b;
        if (DFS(G, a, b)) {
            cout << "yes" << endl;
        } else {
            cout << "no"  << endl;
        }
    }
    return 0;
}

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

using namespace std;

struct Node {
    int color = 0;
    vector<int> next;
} node[100000];

int main() {
    int n, m, q, t1, t2;

    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        cin >> t1 >> t2;
        node[t1].next.push_back(t2);
        node[t2].next.push_back(t1);
    }

    int color = 1;
    queue<int> que;
    while (1) {
        int start = -1;
        for (int i = 0; i < n; i++) {
            if (node[i].color == 0) {
                start = i;
                break;
            }
        }
        if (start == -1) {
            break;
        }
        
        node[start].color = color;
        que.push(start);
        while (!que.empty()) {
            int temp = que.front();
            int size = node[temp].next.size();
            for (int i = 0; i < size; i++) {
                if (node[node[temp].next[i]].color == 0) {
                    node[node[temp].next[i]].color = color;
                    que.push(node[temp].next[i]);
                }
            }
            que.pop();
        }
        color++;
    }

    cin >> q;
    for (int i = 0; i < q; i++) {
        cin >> t1 >> t2;
        if (node[t1].color == node[t2].color && node[t1].color > 0 && node[t2].color > 0) {
            cout << "yes" << endl;
        }
        else {
            cout << "no" << endl;
        }
    }

    return 0;
}