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 <vector>
#include <stack>

//求解图的联通分量

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) {
                color[v] = c;
                S.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;
        G[s].push_back(t);
        G[s].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;
}

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) {
				color[v] = c;
					S.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  u, k, v,q;
	cin >> n >>v;

	for (int i = 0; i < v; i++) {
		cin >> u >> k;
		G[u].push_back(k);
		G[k].push_back(u);
	}
	assignColor();

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

	return 0;
}

C++: #include <vector>
#include <iostream>
using namespace std;
int n, m, q, x, y; int group[111111]; vector<int> f[111111];
int main() {
	scanf("%d%d", &n, &m);
	for(int i = 0; i < n; i++) group[i] = i, f[i].push_back(i);
	for(int i = 0; i < m; i++) {
		scanf("%d%d", &x, &y);
		if(group[x] == group[y]) continue;
		x = group[x], y = group[y];
		if(f[y].size() > f[x].size()) swap(x, y);
		for(int j = f[y].size() - 1; j >= 0; j--) {
			group[f[y][j]] = group[x];
			f[x].push_back(f[y][j]);
			f[y].pop_back();
		}
	}
	scanf("%d", &q);
	for(int i = 0; i < q; i++) {
		scanf("%d%d", &x, &y);
		printf("%s\n", group[x] == group[y] ? "yes" : "no");
	}
	return 0;
}

C++: #include<bits/stdc++.h>
#define ll long long int
#define FOR(i,a,b) for(ll i=(ll)(a);i<(ll)(b);i++)
#define REP(i,n) FOR(i,0,n)
#define REP1(i,n) FOR(i,1,n)

using namespace std;

static const int MAX = 100000;
static const int NIL = -1;

int n, color[MAX];
vector<int> G[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();
    REP(i, G[u].size()) {
      int v = G[u][i];
      if ( color[v] == NIL ) {
        color[v] = c;
        S.push( v );
      }
    }
  }
}

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

int main() {
  int s, t, m, q;

  cin >> n >> m;

  REP(i, m) {
    cin >> s >> t;
    G[s].push_back( t );
    G[t].push_back( s );
  }

  assignColor();

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

  return 0;
}

C++: #include<iostream>
#include<vector>
#include<limits.h>
#include<stack>
#include<string>
using namespace std;

vector< vector<int> > L(100005);
int c[100005]={};

void dfs (int v, int marker){
	if(c[v]!=0){
		return;
	}
	c[v]=marker;
	for (int i=0;i<L[v].size();i++){
		dfs(L[v][i],marker);
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	int n,m,a,b,q,s,t;
	cin >> n >> m;
	
	for (int i=0;i<m;i++){
		cin >> a >> b;
		L[a].push_back(b);
	}
	
	int marker=1;
	for (int i=0;i<n;i++){
		if (c[i]==0){
			dfs(i,marker);
			marker++;
		}
	}
	
	
	cin >> q;
	int d[2][q];
	for (int i=0;i<q;i++){
		cin >> d[i][0];
		cin >> d[i][1]; 
	}
	for (int i=0;i<q;i++){
		if(c[d[i][0]]==c[d[i][1]]){
			cout << "yes" << endl;
		}else{
			cout << "no" << endl;
		}
	}
	return 0;
}