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>
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 i=0;i<n;i++){
		if(color[i] == NIL) dfs(i,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>
#include <cmath>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

#define ll long long
#define vi vector<int>
#define rep(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)

#define NIL -1

int N,M,Q,s,t;
vi T[100005], Color;

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, T[u].size()){
            int v = T[u][i];
            if(Color[v] == NIL){ //色が違っていたらスタックに入れて探索する
                Color[v] = c;
                S.push(v);
            }
        }
    }
}

void AssignColor(){
    int id = 1;

    Color.resize(N,NIL);

    rep(u,N){ //色が違っていたらスタックに入れて探索する
        if(Color[u] == NIL) dfs(u,id++);
    }
}

void solve(int s, int t){
    if(Color[s] == Color[t]) cout << "yes" << endl;
    else cout << "no" << endl;
}

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

    rep(i,M){
        cin >> s >> t;
        T[s].push_back(t);
        T[t].push_back(s);
    };

    AssignColor();

    cin >> Q;

    rep(i,Q){
        cin >> s >> t;
        solve(s, t);
    };
}

C++: #include <bits/stdc++.h>
using ll = long long;
using namespace std;
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for(int i = int(a); i < int(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
const long long INFLL = 1LL << 60;
const int INFINT = 1 << 30;
const long long MOD = 1e9 + 7;

vector<vector<int>> G(101, vector<int>(0));
vector<int> c(101, 0);
vector<int> d(101, 0);
vector<int> f(101, 0);

template <class T> using vec_alias = ::std::vector<T>;

template <class T> void vecout(T V) {
    auto t = V.begin();
    while(t != V.end()) {
        cout << " " << *t++;
        // if(t != V.end()) cout << " ";
    }
    cout << endl;
};

int t = 0;
void dfs(int i) {
    if(c[i]) return;
    c[i] = 1;
    d[i] = ++t;
    for(auto e : G[i])
        dfs(e);
    f[i] = ++t;
}

class node {
  public:
    int dist = -1;
    vector<int> nex;
};

template <template <class> class Container> class union_find {
  protected:
    class node_type;

  public:
    using container_type = Container<node_type>;
    using size_type = typename container_type::size_type;

  protected:
    class node_type {
      public:
        typename union_find::size_type parent;
        typename union_find::size_type size;
    };

    container_type tree;

  public:
    union_find() : tree() {}
    explicit union_find(const size_type size) : tree(size, {0, 1}) {
        for(size_type i = 0; i < size; ++i)
            tree[i].parent = i;
    }

    bool empty() const { return tree.empty(); }
    size_type size() const { return tree.size(); }

    size_type find(size_type x) {
        assert(x < size());
        while(tree[x].parent != x)
            x = tree[x].parent = tree[tree[x].parent].parent;
        return x;
    }
    bool same(const size_type x, const size_type y) {
        assert(x < size());
        assert(y < size());
        return find(x) == find(y);
    }
    size_type size(const size_type x) {
        assert(x < size());
        return tree[find(x)].size;
    }

    ::std::pair<size_type, size_type> unite(size_type x, size_type y) {
        assert(x < size());
        assert(y < size());
        x = find(x);
        y = find(y);
        if(x != y) {
            if(tree[x].size < tree[y].size) ::std::swap(x, y);
            tree[x].size += tree[y].size;
            tree[y].parent = x;
        }
        return {x, y};
    }
};

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n, m, q, s, t;
    cin >> n >> m;
    union_find<vec_alias> uf(n);
    rep(i, m) {
        cin >> s >> t;
        uf.unite(s, t);
    }
    cin >> q;
    rep(i, q) {
        cin >> s >> t;
        cout << (uf.same(s, t) ? "yes" : "no") << "\n";
    }
}