Go: package main

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

// Node 頂点
type Node struct {
	gid  int   // グループID
	edge []int // 隣接辺
}

// NoID グループIDなし
const NoID = -1

// NewNode 頂点の生成
func NewNode() *Node {
	return &Node{gid: NoID, edge: []int{}}
}

func parseNode(nodes []*Node, gid int, queue []int) {
	if len(queue) == 0 {
		return
	}
	var nextQ []int
	for _, id := range queue {
		node := nodes[id]
		if node.gid == NoID {
			node.gid = gid
			for _, edge := range node.edge {
				nextQ = append(nextQ, edge)
			}
		}
	}
	parseNode(nodes, gid, nextQ)
	return
}
func digNode(nodes []*Node, id, gid int) {
	node := nodes[id]
	if node.gid != NoID {
		// 探索済み
		return
	}
	node.gid = gid
	for _, edge := range node.edge {
		digNode(nodes, edge, gid)
	}
	return
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	n, m := eGetInt2(scanner)

	nodes := make([]*Node, n)
	for i := 0; i < n; i++ {
		nodes[i] = NewNode()
	}

	for i := 0; i < m; i++ {
		a, b := eGetInt2(scanner)
		nodes[a].edge = append(nodes[a].edge, b)
		nodes[b].edge = append(nodes[b].edge, a)
	}

	for i := 0; i < n; i++ {
		// 幅優先探索
		// gid := i
		// queue := []int{i}
		// parseNode(nodes, gid, queue)

		// 深さ優先探索
		digNode(nodes, i, i)
	}

	q := eGetInt(scanner)
	for i := 0; i < q; i++ {
		a, b := eGetInt2(scanner)
		if nodes[a].gid == nodes[b].gid {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func eGetInt(scanner *bufio.Scanner) int {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0]
}
func eGetInt2(scanner *bufio.Scanner) (int, int) {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0], t[1]
}

func eGetline(p *bufio.Scanner) string {
	if !p.Scan() {
		if err := p.Err(); err != nil {
			log.Fatal(err.Error())
		}
		return ""
	}
	return p.Text()
}

func eAtoi(s []string) []int {
	ints := make([]int, len(s))
	var err error
	for i, e := range s {
		ints[i], err = strconv.Atoi(e)
		if err != nil {
			log.Fatal(err.Error())
		}
	}
	return ints
}

C++: #include<iostream>
#include<iomanip>
#include<queue>
#include<string>
#include<stack>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<cassert>
#include<ctime>
#include<algorithm>
#include<utility>
#include<map>
#include<set>
#include<vector>
#include<functional>

using namespace std;

#ifdef DEBUG
#define dprintf      printf
#define dout(x)      cout<<#x" = "<<(x)<<endl
#define darray(x,n)    {int i;rep(i,n)cout<<#x"["<<i<<"] = "<<*((x)+i)<<endl;}
#define dloop(i,s,g) for((i)=(s);(i)<(g);(i)++)
#define drep(i,n)    for((i)=0;(i)<(n);(i)++)
#define dstop()      scanf("%*c")
#else
#define dprintf      (1)?0:printf
#define dout(x)
#define darray(x,n)
#define dloop(i,s,g) if(1){}else
#define drep(i,n)    if(1){}else
#define dstop()      if(1){}else
#endif

#define F    first
#define S    second
#define pb   push_back
#define mp   make_pair

#define loop(i,s,g) for((i)=(s);(i)<(g);(i)++)
#define rep(i,n)    for((i)=0;(i)<(n);(i)++)
#define all(x)      (x.begin(),x.end())
#define in(T,...) T __VA_ARGS__; impl(__VA_ARGS__);
#define array(T,id,n) T id[n]; rep(i,n)cin>>id[i];

//#define int long long;
#ifndef int
#define INF  (0x7fffffff)
#else
#define LINF (0x7fffffffffffffff)
#endif

typedef  long long           ll;
typedef  unsigned            ui;
typedef  unsigned long long  ull;
typedef  pair<int,int>       i_i;
typedef  pair<ll,int>        ll_i;
typedef  pair<ll,ll>         ll_ll;
typedef  pair<double,int>    d_i;
typedef  pair<double,double> d_d;
/*
void impl(){};
template <typename T,typename... TS >
void impl(T &head,TS &... tail)
{
  cin>>head;
  impl(tail ...);
}
*/
int e[112345][112345]={};
int sumi[112345]={};
int n,m;

int dfs(int v,int g)
{
  int i;
  int ret=0;
  dout(v);
  if(v==g)
    return 1;
  rep(i,n)
    if(e[v][i]==1 && sumi[i]==0)
      {
	sumi[i]=1;
	ret=dfs(i,g);
	if(ret==1)
	  break;
      }
  return ret;
}
signed main(void)
{
  int i;
  int a,b;
  int q;
  int s,t;
  cin>>n>>m;
  rep(i,m)
    {
      cin>>a>>b;
      e[a][b]=1;
      e[b][a]=1;
    }
  cin>>q;
  rep(i,q)
    {
      cin>>s>>t;
      if(dfs(s,t))
	cout<<"yes"<<endl;
      else
	cout<<"no"<<endl;
    }    
  return 0;
}

C++: //
//  main.cpp
//  connected_components
//
//  Created by ???????????? on 2017/10/22.
//  Copyright ?? 2017 ????????????. All rights reserved.
//

#include <iostream>
#include <stdio.h>
#include <vector>

using namespace std;

#define n_max 100000
//#define vector_max 100000
#define WHITE 0
#define GRAY 1
#define BLACK 2

bool found;
int n, target, t = 0;
int color[n_max], d[n_max], f[n_max];
vector<int> G[n_max];

void encode_graph_list(){
    int i, id, node, f;
    
    scanf("%d", &n);
    scanf("%d", &node);
    
    for (i = 0; i < node; i++){
        scanf("%d", &id);
        scanf("%d", &f);
        G[id].push_back(f);
    }
    
}

void dfs(int u){
//    found = false;
//    if(target == u) {
//        found = true;
//        return;
//    }
    color[u] = GRAY;
    d[u] = ++t;
    for (int v = 0; v < G[u].size(); v++){
        int t = G[u][v];
        if(color[t] == WHITE){
            dfs(t);
        }
    }
    color[u] = BLACK;
    f[u] = ++t;
}

void dfs_init(int start){
    for(int i = 0; i < n ; i++){
        color[i] = WHITE;
    }
    dfs(start);
}



int main(int argc, const char * argv[]) {
    int qs, i, id;
    encode_graph_list();
    scanf("%d", &qs);
    for (i = 0; i < qs; i++){
        scanf("%d %d", &id, &target);
        dfs_init(id);
        if(color[target] == color[id]) cout << "yes" <<endl;
        else cout << "no"<<endl;
    }
//    std::cout << "Hello, World!\n";
    return 0;
}

C++: #include<bits/stdc++.h>
#include<stdio.h>
using namespace std;

#define ll                  long long
#define scl(n)              scanf("%lld", &n)
#define fr(i,n)             for (ll i=0;i<n;i++)
#define fr1(i,n)            for(ll i=1;i<=n;i++)
#define pfl(x)              printf("%lld\n",x)
#define endl 	            "\n"
#define pb                  push_back
#define l(s)                s.size()
#define asort(a)            sort(a,a+n)
#define dsort(a)            sort(a,a+n,greater<int>())
#define vasort(v)           sort(v.begin(), v.end());
#define vdsort(v)           sort(v.begin(), v.end(),greater<int>());
#define pn                  printf("\n")
#define md                  10000007

ll n;
vector<ll>v[1000005];
ll cnt=1;
bool vis[1000005];
ll clr[1000005];
queue<ll>q;
void bfs(ll s, ll d)
{
    q.push(s);
    clr[s]=d;
    while(!q.empty())
    {
         ll p=q.front(); q.pop();
         for(ll i=0;i<v[p].size();i++)
         {
             ll u=v[p][i];
             if(clr[u]==-1)
             {
                 q.push(u);
                 clr[u]=d;
             }
         }
    }
}

void colour( )
{
    fr(i,1000000)clr[i]=-1;

    fr(i,n)if(clr[i]==-1)bfs(i, cnt++);
}
int main()
{
    ll m,t,b,c,d,i,j,k,x,y,z,l,q,r;

      ll cnt=0,ans=0;
      scl(n);scl(m);

      fr(i,m)
      {
          cin>>x>>y;
          v[x].pb(y);
          v[y].pb(x);
      }
      colour();

      cin>>q;
      while(q--)
      {
          cin>>x>>y;
          if(clr[x]==clr[y])cout<<"yes"<<endl;
          else cout<<"no"<<endl;
      }
return 0;
}