Go: package main

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

var (
	n     int
	G     [100000][]int
	color [100000]*int
)

func dfs(r int, c int) {
	S := Stack{}
	S.Push(r)
	color[r] = &c
	for !S.IsEmpty() {
		u := S.Pop()
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == nil {
				color[v] = &c
				S.Push(v)
			}
		}
	}
}

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

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan()
	n, _ = strconv.Atoi(sc.Text())
	sc.Scan()
	r, _ := strconv.Atoi(sc.Text())

	for i := 0; i < r; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	assignColor()
	sc.Scan()
	qNum, _ := strconv.Atoi(sc.Text())
	for i := 0; i < qNum; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

// Stack is Stack
type Stack struct {
	stack []int
}

// Push new value
func (stack *Stack) Push(val int) {
	stack.stack = append(stack.stack, val)
}

// Pop new value
func (stack *Stack) Pop() int {
	val := stack.stack[len(stack.stack)-1]
	stack.stack = stack.stack[0 : len(stack.stack)-1]
	return val
}

// IsEmpty return true when stack is empty
func (stack *Stack) IsEmpty() bool {
	return len(stack.stack) == 0
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MOD = 1e9 + 7;
const int inf = 1e9;
const ll INF = 1e18;
const double pi = 3.14159265358979323846;
#define rep(i, n) for (int i = 0; i < n; i++)
using Graph = vector<vector<int>>;
using pint = pair<int, int>;
int dx[4] = { 1, 0, -1, 0 }, dy[4] = { 0, 1, 0, -1 };

int main() {
    int n, m;
    cin >> n >> m;
    Graph g (n);
    rep (i, m) {
        int a, b;
        cin >> a >> b;
        g[a].push_back (b);
        g[b].push_back (a);
    }
    //BFSを行う
    int color[n];
    rep (i, n) color[i] = -1;
    int now = 0;
    rep (i, n) {
        if (color[i] == -1) {
            queue<int> q;
            q.push (i);
            color[i] = now;
            while (!q.empty()) {
                int v = q.front();
                q.pop();
                for (auto p : g[v]) {
                    if (color[p] != -1) continue;
                    color[p] = now;
                    q.push (p);
                }
            }
            now++;
        }
    }
    int q;
    cin >> q;
    rep (i, q) {
        int s, t;
        cin >> s >> t;
        if (color[s] == color[t]) cout << "yes"
                                       << "\n";
        else
            cout << "no"
                 << "\n";
    }
}

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

using namespace std;

class UnionFind {
public:
    vector<int> par, num;

    explicit UnionFind(int N) {
        par.resize(N);
        iota(par.begin(), par.end(), 0);
        num.assign(N, 1);
    }

    int find(int v) {
        return (par[v] == v) ? v : (par[v] = find(par[v]));
    }

    void unite(int u, int v) {
        u = find(u), v = find(v);
        if (u == v) return;

        if (num[u] < num[v]) swap(u, v);
        num[u] += num[v];
        par[v] = u;
    }

    bool same(int u, int v) { return find(u) == find(v); }
    bool ispar(int v) { return v == find(v); }
    int size(int v) { return num[find(v)]; }
};

int main() {
    int N, M;
    cin >> N >> M;

    UnionFind uf(N);
    for (int i = 0; i < M; ++i) {
        int u, v;
        cin >> u >> v;
        uf.unite(u, v);
    }

    int Q;
    cin >> Q;
    for (int q = 0; q < Q; ++q) {
        int u, v;
        cin >> u >> v;
        cout << (uf.same(u, v) ? "yes" : "no") << endl;
    }
    return 0;
}