Go: package main

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

var (
	n     int
	G     [100000][]int
	color [100000]*int
)

func dfs(r int, c int) {
	S := Stack{}
	S.Push(r)
	color[r] = &c
	for !S.IsEmpty() {
		u := S.Pop()
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == nil {
				color[v] = &c
				S.Push(v)
			}
		}
	}
}

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

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan()
	n, _ = strconv.Atoi(sc.Text())
	sc.Scan()
	r, _ := strconv.Atoi(sc.Text())

	for i := 0; i < r; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	assignColor()
	sc.Scan()
	qNum, _ := strconv.Atoi(sc.Text())
	for i := 0; i < qNum; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

// Stack is Stack
type Stack struct {
	stack []int
}

// Push new value
func (stack *Stack) Push(val int) {
	stack.stack = append(stack.stack, val)
}

// Pop new value
func (stack *Stack) Pop() int {
	val := stack.stack[len(stack.stack)-1]
	stack.stack = stack.stack[0 : len(stack.stack)-1]
	return val
}

// IsEmpty return true when stack is empty
func (stack *Stack) IsEmpty() bool {
	return len(stack.stack) == 0
}

C++: #define _USE_MATH_DEFINES
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <clocale>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#define IOS ios::sync_with_stdio(false); cin.tie(0);
#define FOR(i, s, n) for(int i = (s), i##_len=(n); i < i##_len; ++i)
#define FORS(i, s, n) for(int i = (s), i##_len=(n); i <= i##_len; ++i)
#define VFOR(i, s, n) for(int i = (s); i < (n); ++i)
#define VFORS(i, s, n) for(int i = (s); i <= (n); ++i)
#define REP(i, n) FOR(i, 0, n)
#define REPS(i, n) FORS(i, 0, n)
#define VREP(i, n) VFOR(i, 0, n)
#define VREPS(i, n) VFORS(i, 0, n)
#define RFOR(i, s, n) for(int i = (s), i##_len=(n); i >= i##_len; --i)
#define RFORS(i, s, n) for(int i = (s), i##_len=(n); i > i##_len; --i)
#define RREP(i, n) RFOR(i, n, 0)
#define RREPS(i, n) RFORS(i, n, 0)
#define ALL(v) (v).begin(), (v).end()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(ALL(v), greater<decltype(v[0])>())
#define SZ(x) ((int)(x).size())
#define PB push_back
#define MP make_pair
#define MT make_tuple
#define BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(ALL(v)), v.end())

using ll = long long;
using Pi_i = pair<int, int>;
using VB = vector<bool>;
using VC = vector<char>;
using VD = vector<double>;
using VI = vector<int>;
using VLL = vector<ll>;
using VS = vector<string>;
using VSH = vector<short>;

const int MOD = 1000000007;
const int INF = 1000000000;
const int NIL = -1;

template<class T, class S>
bool chmax(T &a, const S &b){
    if(a < b){
        a = b; return true;
    }
    return false;
}
template<class T, class S>
bool chmin(T &a, const S &b){
    if(b < a){
        a = b; return true;
    }
    return false;
}


class UnionFind{
    vector<int> par;
    vector<int> rank;

public:
    UnionFind(){}
    UnionFind(int n): par(n), rank(n){
        REP(i, n){
            par[i] = i;
            rank[i] = 0;
        }
    }

    void resize(int n){
        int m = par.size();
        par.resize(n);
        rank.resize(n, 0);
        FOR(i, m, n) par[i] = i;
    }

    int find(int x){
        if(x == par[x]) return x;
        else return par[x] = find(par[x]);
    }

    void unit(int x, int y){
        x = find(x);
        y = find(y);
        if(x == y) return;

        if(rank[x] < rank[y]){
            par[x] = y;
        }else{
            par[y] = x;
            if(rank[x] == rank[y]) ++rank[x];
        }
    }

    bool same(int x, int y){
        return find(x) == find(y);
    }
};
int n;
UnionFind UF;
vector<VI> edge;
VB visited;

void dfs(int u){
    visited[u] = true;
    for(int v: edge[u]){
        if(!visited[v]){
            UF.unit(u, v);
            dfs(v);
        }
    }
}

int main(){
    int m; cin >> n >> m;
    edge.resize(n);
    visited.resize(n, false);
    REP(i, m){
        int u, v; cin >> u >> v;
        edge[u].PB(v); edge[v].PB(u);
    }
    UF.resize(n);
    REP(i, n){
        if(!visited[i]) dfs(i);
    }
    int q; cin >> q;
    REP(i, q){
        int s, t; cin >> s >> t;
        cout << (UF.same(s, t) ? "yes" : "no") << "\n";
    }
    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;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using ll = long long;

static const int NIL = -1;

int main()
{
    int n;
    int m;
    cin >> n >> m;

    vector<int> color(n, NIL);
    vector<vector<int>> node_list(n, vector<int>(0));

    int v1, v2;
    rep(i, m)
    {
        cin >> v1 >> v2;
        node_list.at(v1).push_back(v2);
        node_list.at(v2).push_back(v1);
    }

    int count = 0;
    auto paint_color = [&](int s) {
        if (color.at(s) != NIL)
        {
            
            return;
        }

        queue<int> q;
        q.push(s);
        color.at(s) = count;

        while (!q.empty())
        {
            v1 = q.front();
            q.pop();
            
            for (size_t i = 0; i < node_list.at(v1).size(); i++)
            {
                if (color.at(node_list.at(v1).at(i)) == NIL)
                {
                    q.push(node_list.at(v1).at(i));
                    color.at(node_list.at(v1).at(i)) = count;
                }
            }
        }

        count++;
    };

    rep(i, n)
    {
        paint_color(i);
    }

    int w;
    cin >> w;
    rep(i, w)
    {
        cin >> v1 >> v2;
        if(color.at(v1)==color.at(v2))
        {
            cout << "yes" << endl ;
        }
        else
        {
            cout << "no" << endl ;
        }
        
    }
    
    return 0 ;
}