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++: // http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_11_A
// Graph I - Connected Components

#define SUBMIT

#include <utility>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <vector>
#include <limits>
#include <numeric>
#include <functional>
#include <set>
#include <cmath>
#include <cstring>
#include <climits>
#include <memory>

using namespace std;
using ui64 = unsigned long long;
using i64 = long long;

const int NIL = -1;
const ui64 MAX_N = 100000;

vector<int> adj[MAX_N];
int assigned_group_ids[MAX_N];
int n, m, q;
int group_id;

void dfs(int u, int id) {
    assigned_group_ids[u] = id;
    // search adj nodes
    for (const auto& v : adj[u]) {
        if (assigned_group_ids[v] == NIL) dfs(v, id);
    }
}

void assign_group() {
    memset(assigned_group_ids, NIL, sizeof(assigned_group_ids));
    group_id = 0;

    for (int u = 0; u < n; ++u) {
        if (assigned_group_ids[u] == NIL) {
            dfs(u, group_id);
            group_id++;
        }
    }
}

int main() {
    memset(adj, 0, sizeof(adj));
    cin >> n >> m;

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

    assign_group();

    cin >> q;

    for (int i = 0; i < q; ++i) {
        int s, t;
        cin >> s >> t;
        if (assigned_group_ids[s] == assigned_group_ids[t]) cout << "yes" << endl;
        else cout << "no" << endl;
    }

    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
const int MAX = 100000;
const int NIL = -1;
int n;
vector<int> G[MAX];
int color[MAX];
void dfs(int r,int c) {
    if(color[r] == NIL) color[r] = c;
    for(int i = 0;i < G[r].size();i++) {
        int v = G[r][i];
        if(color[v] == NIL) dfs(v,c);
    }
}
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;
    scanf("%d%d",&n,&m);
    for(int i = 0;i < m;++i) {
        scanf("%d%d",&s,&t);
        G[s].push_back(t);
        G[t].push_back(s);
    }
    assignColor();
    scanf("%d",&q);
    for(int i = 0;i < q;++i) {
        scanf("%d%d",&s,&t);
        if(color[s] == color[t]) printf("yes\n");
        else 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) {
   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 >> s >> 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 <vector>
#include <algorithm>
#include <numeric>
#include <queue>
#include <stack>
#include <map>
#define FOR(i,b,e) for(int i=b;i<e;i++)
#define REP(i,n) FOR(i,0,n)
using namespace std;

const int N = 100000;
int n, m, q;
vector<int> M[N];
bool V[N];

int bfs(int u, int v) {
  int s;
  queue<int> q;
  REP(i, n) V[i] = false;

  s = u;
  q.push(s);
  V[s] = true;

  while (!q.empty() && !V[v]) {
    s = q.front(); q.pop();
    REP(i, M[s].size()) {
      int t = M[s][i];
      if (!V[t]) {
        q.push(t);
        V[t] = true;
      }
    }
  }

  return V[v];
}

int main() {
	cin.tie(0);
 	ios::sync_with_stdio(false);

  cin >> n >> m;
  REP(i, m) {
    int u, v;
    cin >> u >> v;
    M[u].push_back(v);
    M[v].push_back(u);
  }

  cin >> q;
  REP(i, q) {
    int u, v;
    string answer;
    cin >> u >> v;
    answer = bfs(u, v) ? "yes" : "no";
    cout << answer << endl;
  }
}

C++: #include <iostream>
#include <vector>
#include <queue>
static const int MAX=100000;
using namespace std;
vector<int> follow[MAX];
int color[MAX];  //-1 represent No Visitedvoid 
bfs(int i,int c){    queue<int> Q;    Q.push(i);color[i]=c;    
while(!Q.empty())  
  {        int p=Q.front();Q.pop();        for(int j=0;j<follow[p].size();j++)        {            if(color[follow[p][j]]!=-1) continue;            //else            Q.push(follow[p][j]); color[follow[p][j]]=color[p];        }    }}
int main(){   int n,m;   cin>>n>>m;   for(int i=0;i<n;i++) color[i]=-1;   for(int i=0;i<m;i++)   {       int a,b;       cin>>a>>b;       follow[a].push_back(b);       follow[b].push_back(a);   }   int c=0;   for(int i=0;i<n;i++)   {       if(color[i]==-1)       {           bfs(i, c);           c++;       }   }   int order_num;cin>>order_num;   for(int i=0;i< order_num;i++)   {       int a,b;       cin>>a>>b;       if(color[a]==color[b]) cout<<"yes"<<endl;       else cout<<"no"<<endl;   }}