Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

func newGraph(nNodes int) *Graph {
	g := Graph{}
	g.nodes = make([]*GraphNode, nNodes)
	for iNode := 0; iNode < len(g.nodes); iNode++ {
		g.nodes[iNode] = &GraphNode{}
		g.nodes[iNode].key = GraphNodeKey(iNode)
	}
	return &g
}

var infty = 1000000000

type GraphNodeKey int

// GraphNode is a node for undirected graph
type GraphNode struct {
	key       GraphNodeKey
	adjacents []*GraphNode
	visited   bool
	d, f      int
	parent    *GraphNode
	cc        int
}

func (g *Graph) setAdjacent(l, r GraphNodeKey) {
	g.nodes[l].adjacents = append(g.nodes[l].adjacents, g.nodes[r])
}

// Graph is a undirected graph
type Graph struct {
	nodes []*GraphNode
}

func (g *Graph) initialize() {
	for iNode := 0; iNode < len(g.nodes); iNode++ {
		g.nodes[iNode].visited = false
		g.nodes[iNode].d = infty
		g.nodes[iNode].f = infty
		g.nodes[iNode].parent = nil
		g.nodes[iNode].cc = -1 // 22.3-12
	}
}

type QueueEntry struct {
	node *GraphNode
	next *QueueEntry
}

type Queue struct {
	head, tail *QueueEntry
}

func (q *Queue) enqueue(node *GraphNode) {
	entry := QueueEntry{}
	entry.node = node

	if q.tail == nil {
		q.head = &entry
		q.tail = &entry
		return
	}

	q.tail.next = &entry
	q.tail = q.tail.next
}

func (q *Queue) dequeue() *QueueEntry {
	if q.head == nil {
		return nil
	}
	poped := q.head
	q.head = q.head.next
	if q.head == nil {
		q.tail = nil
	}
	return poped
}

func (q *Queue) isEmpty() bool {
	return q.head == nil
}

var time = 0

func fillDistancesByDepthFirstSearch(g *Graph) {
	g.initialize()
	time = 0
	cc := 0

	for _, u := range g.nodes {
		if !u.visited {
			dfsVisit(g, u, cc)
			cc++
		}
	}
}

func dfsVisit(g *Graph, u *GraphNode, cc int) {
	time++
	u.d = time
	u.cc = cc

	u.visited = true
	for _, v := range u.adjacents {
		if !v.visited {
			v.parent = u
			dfsVisit(g, v, cc)
		}
	}
	time++
	u.f = time
}

func main() {
	scanner.Split(bufio.ScanWords)

	nUsers := nextInt()
	nEdges := nextInt()
	graph := newGraph(nUsers)
	for iEdge := 0; iEdge < nEdges; iEdge++ {
		l := GraphNodeKey(nextInt())
		r := GraphNodeKey(nextInt())
		graph.setAdjacent(l, r)
		graph.setAdjacent(r, l)
	}

	fillDistancesByDepthFirstSearch(graph)

	nQueries := nextInt()
	for iQuery := 0; iQuery < nQueries; iQuery++ {
		l := GraphNodeKey(nextInt())
		r := GraphNodeKey(nextInt())

		// fmt.Println(graph.nodes[l].d, graph.nodes[r].d, graph.nodes[r].f, graph.nodes[l].f)
		if graph.nodes[l].cc == graph.nodes[r].cc {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

C++: #include <iostream>
#include <string>
#include <stack>
#include <queue>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <algorithm>

#include <cstdio>

using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define repc(i, s, n) for (int i = (s); i <= (n); i++)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; i--)
#define rrepc(i, s, n) for (int i = (s); i >= (n); i--)
#define print_array(ary, size) cout << ary[0]; rep1(i, 1, size - 1) cout << ' ' << ary[i]; cout << endl;
typedef long long ll;
typedef unsigned long long ull;

vector<int> SNS[100000];
int Group[100000] = { 0 };

int main()
{
	int n, m, q, s, t;
	int man1, man2;
	int grNo = 1;
	int current, next;
	queue<int> Q;
	vector<int>::iterator it;
	
	cin >> n >> m;
	rep(i, m) {
		cin >> man1 >> man2;
		SNS[man1].push_back(man2);
		SNS[man2].push_back(man1);
	}

	rep(i, n) {
		if (Group[i] == 0) {
			Q.push(i);
			Group[i] = grNo;

			while (!Q.empty()) {
				current = Q.front();

				for (it = SNS[current].begin(); it != SNS[current].end(); it++) {
					next = *it;
					if (Group[next] == 0) {
						Q.push(next);
						Group[next] = grNo;
					}
				}

				Q.pop();
			}

			grNo++;
		}
	}

	cin >> q;
	rep(i, q) {
		cin >> s >> t;
		if (Group[s] == Group[t]) cout << "yes" << endl;
		else cout << "no" << endl;
	}

	return 0;
}

C++: #include <stdio.h>
int ancestor[10];
int find(int x){
    if(ancestor[x]==x)return x;
    return ancestor[x]=find(ancestor[x]);
}
int min(int a,int b){
    if(a<b)return a;
    return b;
}
int max(int a,int b){
    if(a>b)return a;
    return b;
}
int main(){
    int n,q,m,temp,x,y;
    scanf("%d%d",&n,&m);
    for(int i=0;i<n;i++)ancestor[i]=i;
    for(int i=0;i<m;i++){
        scanf("%d%d",&x,&y);
        temp=find(x);
        q=find(y);
        ancestor[max(temp,q)]=min(temp,q);
    }
    scanf("%d",&q);
    for(int i=0;i<q;i++){
        scanf("%d%d",&x,&y);
        if(find(x)!=find(y))printf("no\n");
        else printf("yes\n");
    }
}

C++: #include <bits/stdc++.h>

using namespace std;

typedef long long int ll;
typedef pair<ll, ll> pll;

#define FOR(i, n, m) for(ll (i)=(m);(i)<(n);++(i))
#define REP(i, n) FOR(i,n,0)
#define OF64 std::setprecision(10)

const ll MOD = 1000000007;
const ll INF = (ll) 1e15;

struct Vertex {
    vector<ll> node;
};

Vertex V[100005];
bool U[100005];
ll Parent[100005];

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll N, M;
    cin >> N >> M;
    REP(_, M) {
        ll a, b;
        cin >> a >> b;
        V[a].node.push_back(b);
        V[b].node.push_back(a);
    }

    REP(i, N) {
        Parent[i] = i;
    }
    memset(U, 0, sizeof(U));

    REP(i, N) {
        if (U[i])
            continue;
        queue<ll> q;
        q.push(i);
        U[i] = true;
        while (!q.empty()) {
            ll t = q.front();
            q.pop();
            for (auto &n:V[t].node) {
                if (U[n])
                    continue;
                Parent[n] = i;
                q.push(n);
                U[n] = true;
            }
        }
    }

    ll Q;
    cin >> Q;
    REP(_, Q) {
        ll s, t;
        cin >> s >> t;
        if (Parent[s] == Parent[t])
            cout << "yes" << endl;
        else
            cout << "no" << endl;
    }
    
    return 0;
}

C++: #include <iostream>
#include <math.h>
#include <vector>
#include <algorithm>

using namespace std;
#define MAX 100005
#define NIL -1

vector<int> V[MAX];
int color[MAX];


void search(int v, int c) {
	if (color[v] != NIL)return;
	color[v] = c;
	for (int i = 0; i < V[v].size(); i++) {
		search(V[v][i], c);
	}
}

int main() {
	int n, m;
	cin >> n >> m;
	V->reserve(n);
	for (int i = 0; i < m; i++) {
		int s, t;
		cin >> s >> t;
		V[s].push_back(t);
		V[t].push_back(s);
	}

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

	int q;
	cin >> q;
	for (int i = 0; i < q; i++) {
		int s, t;
		cin >> s >> t;
		if (color[s] == color[t])cout << "yes\n";
		else cout << "no\n";
	}

	return 0;
}

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];
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) {
        S.push(v);
        color[v] = c;
      }
    }
  }
}

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

int main() {
  int m, u, v, q;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    cin >> u >> v;
    G[u].push_back(v);
    G[v].push_back(u);
  }

  assignColor();

  cin >> q;
  for (int i = 0; i < q; i++) {
    cin >> u >> v;
    if (color[u] == color[v]) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  }

  return 0;
}