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++: #include<stack>
#include<queue>
#include<vector>
#include<iostream>
#include<algorithm>
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<iostream>
#include<stack>
#include<vector>

using namespace std;

#define MAX 100000
#define NIL -1

int n;
int color[MAX];
vector<int> G[MAX];


void dfs(int u, int id){
  
  stack<int> S;
  S.push(u);
  color[u] = id;

  int present;
  while( !S.empty() ){
    present = S.top();
    S.pop();

    for(int i=0;i<G[present].size();i++){
      int v = G[present][i];
      if( color[v] == NIL ){
        color[v] = id;
        S.push(v);
      }    
    }  
  }
}

void assignColor(){
 
  for(int i=0;i<n;i++){
    color[i] = NIL;
  } 

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

int main(void){

  int m;
  cin >> n >>  m;

  int u,v;
  for(int i=0;i<m;i++){
    cin >> u >> v;
    G[u].push_back(v);
    G[v].push_back(u);
  }

  assignColor();

  int q;
  cin >> q;

  int s,t;
  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<stdio.h>
#include<queue>

#define MAX 100000

int G[MAX+1][MAX+1];
int n, m;
std::queue<int> Q;

bool bfs(int src, int dest) {
    bool C[MAX];
    for (int i = 0; i < n; ++i) C[i] = false;

    Q.push(src);
    while(!Q.empty()) {
        int cur = Q.front();Q.pop();
        for (int i = 0; i < n; ++i) {
            if (G[cur][i] == 0) continue;
            if (C[i]) continue;
            if (i == dest) return true;
            Q.push(i);
            C[i] = true;
        }
    }

    return false;
}

int main() {
    scanf("%d %d", &n, &m);
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            G[i][j] = 0;
        }
    }
    //for (int i = 0; i < m; ++i) {
    //    int u,k;
    //    scanf("%d %d", &u, &k);
    //    G[u][k] = 1;
    //    G[k][u] = 1;
    //}

    //int q;
    //scanf("%d", &q);
    //for (int i = 1; i <= q; ++i) {
    //    int s,d;
    //    scanf("%d %d", &s, &d);
    //    bfs(s, d) ? printf("yes\n") : printf("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)
{
    // 双方向に行ける頂点の集団の色をcとして，rを始点とする
    stack<int> S;
    S.push(r);
    color[r] = c;
    while(!S.empty()) {
        // rから行けるところなくなるまで深さ優先探索する
        int u = S.top();
        S.pop();
        for (int i = 0; i < G[u].size(); i++) {  // G[u].size()はuが行く可能性のある頂点の数だけ
            int v = G[u][i];  // vはuが行く可能性のある頂点
            if (color[v] == NIL) {
                // 配列colorで行く可能性のある頂点の色が埋まってなかったら
                // 行く可能性のある頂点の色をc(= id)とする
                // そしてvをSに格納する
                color[v] = c;
                S.push(v);
            }
        }
    }
}

void assignColor()
{
    // 双方向に行ける集団の色を同じにする
    int id = 1;
    for (int i = 0; i < n; i++) {
        color[i] = NIL;  // 配列colorを初期化
    }
    for (int u = 0; u < n; u++) {
        // 初期化したcolorに対して，深さ優先探索をする
        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;
        // 有向グラフの隣接リスト
        // s->tとt->s
        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<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++); //それぞれの連結な部分グラフに番号（色）を与える
    }
}

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;
}