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 <assert.h>
using namespace std;
#define MAX_V 100000

int represent[MAX_V];
int status[MAX_V];

int findRepresent(int x)
{
    if (represent[x] == x) {
        return x;
    } else {
        represent[x] = findRepresent(represent[x]);
        return represent[x];
    }
}

void unite(int x, int y)
{
    x = findRepresent(x);
    y = findRepresent(y);
    if (x == y)
        return;
    if (status[x] < status[y])
        swap(x, y);
    assert(status[x] >= status[y]);
    represent[y] = x;
    if (status[x] == status[y])
        status[x]++;
}

bool same(int x, int y)
{
    return (findRepresent(x) == findRepresent(y));
}

int main()
{
    for (int i = 0; i < MAX_V; ++i) {
        represent[i] = i;
        status[i] = 0;
    }

    int n, m;
    cin >> n >> m;
    for (int i = 0; i < m; ++i) {
        int a, b;
        cin >> a >> b;
        unite(a, b);
    }
    int q;
    cin >> q;
    for (int i = 0; i < q; ++i) {
        int from, to;
        cin >> from >> to;
        cout << (same(from, to)? "yes" : "no") << '\n';
    }
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <stack>
using namespace std;
static const int MAX = 1000000;
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[t].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>
using namespace std;
#include<stdio.h>

int *P;

int root(int a)
{
    if(P[a] == a) return a;
    P[a] = root(P[a]);
    return P[a]; 
}

void join(int a, int b){ int x = root(a), y = root(b); x = P[y]; }

bool same(int a, int b){ return (root(a) == root(b) ? true : false); }

int main()
{
    int i, n, m, a, b, q;
    scanf("%d %d", &n, &m);
    P = new int [n];
    for(i = 0; i < n; i++) P[i] = i;

    for(i = 0; i < m; i++) join(a, b);

    scanf("%d", &q);
    for(i = 0; i < q; i++){
        scanf("%d %d", &a, &b);
        if(same(a, b)){ printf("yes\n"); }else{ printf("no\n"); }
    }
    delete [] P;
    return 0; 
}

C++: #include<bits/stdc++.h>
using namespace std;
#define int long long
struct UnionFind{
  int n;
  vector<int> p,r;
  UnionFind(){}
  UnionFind(int n):n(n){init();}
  void init(){
    p.clear();
    r.clear();
    p.resize(n);
    r.resize(n,1);
    for(int i=0;i<n;i++) p[i]=i;
  }
  int find(int x){
    return (p[x]==x?x:p[x]=find(p[x]));
  }
  bool same(int x,int y){
    x=find(x);y=find(y);
    return x==y;
  }
  void unite(int x,int y){
    x=find(x);y=find(y);
    if(x==y) return;
    if(r[x]<r[y]) swap(x,y);
    p[y]=x;
    r[x]+=r[y];
  }
};
signed main(){
  int n,m;
  cin>>n>>m;
  UnionFind uf(n);
  for(int i=0;i<m;i++){
    int s,t;
    cin>>s>>t;
    uf.unite(s,t);
  }
  int q;
  cin>>q;
  for(int i=0;i<q;i++){
    int s,t;
    cin>>s>>t;
    cout<<(uf.same(s,t)?"yes":"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 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);
    }

    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;
}