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 <bits/stdc++.h>
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)
#define len(x) ((int)(x).size())
#define mp make_pair
#define eb emplace_back
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;
constexpr int MAX = 1e6;
constexpr int NIL = -1;
int n;
vi G[MAX];
vi color(MAX, NIL);
inline void dfs(int r, int c) {
	deque<int> S;
	S.eb(r);
	color[r] = c;
	int u, v;
	while(!S.empty()) {
		u = S.back(); S.pop_back();
		rep(i, 0, len(G[u])) {
			v = G[u][i];
			if(color[v] == NIL) {
				color[v] = c;
				S.eb(v);
			}
		}
	}
}
inline void assignColor() {
	int id = 0;
	rep(u, 0, n) {
		if(color[u] == NIL) dfs(u, ++id);
	}
}
int main() {
	int m;
	cin >> n >> m;
	int s, t;
	rep(i, 0, m) {
		cin >> s >> t;
		G[s].eb(t);
		G[t].eb(s);
	}
	assignColor();
	int q; cin >> q;
	rep(i, 0, q) {
		cin >> s >> t;
		P(color[s] == color[t] ? "yes" : "no");
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <climits>
#include <cmath>
#include <algorithm>
#include <utility>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#define MAX 100000
#define INFTY 1<<30 // 2^30
using namespace std;
typedef long long llong;
 
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 assingColor()
{
  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[t].push_back(s);
  }
 
  assingColor();
 
  cin >> q;
  for(int i = 0; i < q; i++)
  {
    cin >> s >> t;
    cout << ((color[s] == color[t]) ? "yes" : "no") << endl;
  }
  return 0;
}

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

using namespace std;

int n, color[10000];
vector<int> G[10000];

void dfs (int r, int c) {

    int i, u, v;

    stack<int> S;
    S.push(r);
    color[r] = c;

    while (!S.empty()) {
        u = S.top();
        S.pop();
        for (i = 0; i < G[u].size(); i++) {
            v = G[u][i];
            if (color[v] == -1) {
                color[v] = c;
                S.push(v);
            }
        }
    }

}

void assignColor () {

    int id = 1, i, u;

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

}

int main () { 

    int s, t, m, q, i;

    cin >> n >> m;

    for (i = 0; i < m; i++) {
        cin >> s >> t;
        G[s].push_back(t);
        G[t].push_back(s);
    }

    assignColor ();

    cin >> q;

    for (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<stdio.h>
#include<vector>
#include<queue>
#define MAX 100000
using namespace std;
int d[MAX];

int n;
vector <int> M[MAX];


int tail;



void BFS(int s,int t) {
	queue <int>Q;
	Q.push(s);
	d[s] = t;
	while (!Q.empty()) {
		s = Q.front();
		Q.pop();
		for (int j = 0; j < M[s].size(); j++) {
				
				if (d[M[s][j]] == -1) {
					d[M[s][j]] = t;
					Q.push(M[s][j]);
				}
		}

	}
}


int main() {
	int  m, s, t, q;
	scanf("%d %d", &n, &m);

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

	for (int i = 0; i < n; i++) {
		d[i] = -1;
	}
	int count = 0;
	for (int i = 0; i < n; i++) {
		if (d[i] == -1) {
			count++;
			BFS(i, count);
		}
	}
	cin >>q;
	for (int i = 0; i < q; i++) {
		int s2, t2;
		scanf("%d %d", &s2, &t2);
		if (d[s2] == d[t2]) {
			printf("yes\n");
		}
		else {
			printf("no\n");
		}
		
		
	}
	
	return 0;
}