Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N, M := sc.nextInt(), sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < M; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	group := make([]int, N)
	for i := 0; i < N; i++ {
		group[i] = -1
	}
	var dfs func(cur int)
	dfs = func(cur int) {
		for i := 0; i < len(G[cur]); i++ {
			next := G[cur][i]
			if group[next] == -1 {
				group[next] = group[cur]
				dfs(next)
			}
		}
	}
	num := 0
	for i := 0; i < N; i++ {
		if group[i] == -1 {
			group[i] = num
			dfs(i)
			num++
		}
	}

	Q := sc.nextInt()
	for i := 0; i < Q; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		if group[s] == group[t] {
			fmt.Fprintln(wtr, "yes")
		} else {
			fmt.Fprintln(wtr, "no")
		}
	}
	wtr.Flush()
}

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";
    }
}