Go: package main

import (
	"bufio"
	"container/list"
	"fmt"
	"os"
	"strconv"
)

//util
var sc = bufio.NewScanner(os.Stdin)

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

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	n := len(list)
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list[0 : n-1] {
		buf.Write([]byte(fmt.Sprintf("%d ", v)))
	}
	buf.Write([]byte(fmt.Sprintf("%d\n", list[n-1])))
	buf.Flush()
}

func max(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func min(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

//solve
const (
	MAX = 100000
	NIL = -1
)

var (
	n, m, q, s, t int
	G             [MAX][]int //連結リスト
	color         [MAX]int
)

func dfs(r int, c int) {
	S := list.New()
	S.PushFront(r)
	color[r] = c
	for S.Len() != 0 {
		u := S.Remove(S.Front()).(int)
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == NIL {
				color[v] = c
				S.PushFront(v)
			}
		}
	}
}

//幅優先探索で、頂点を色付け
func assignColor() {
	id := 1
	for i := 0; i < n; i++ {
		color[i] = NIL
	}
	for i := 0; i < n; i++ {
		if color[i] == NIL {
			id++
			dfs(i, id)
		}
	}
}

func main() {
	sc.Split(bufio.ScanWords)
	n, m = nextInt(), nextInt()
	for i := 0; i < m; i++ {
		s, t = nextInt(), nextInt()
		if i == 0 {
			G[s] = make([]int, 0)
			G[t] = make([]int, 0)
		}
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)

	}
	assignColor()
	q = nextInt()
	for i := 0; i < q; i++ {
		s, t = nextInt(), nextInt()
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}

}

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<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#define Lens 100005

using namespace std;
int n, m, q;
vector<int> A[Lens];
queue<int>	Q;

int Find(int s, int t)
{
	Q.push(s);
	while (!Q.empty())
	{
		s = Q.front();
		Q.pop();
		for (int j = 0; j < A[s].size(); j++)
		{
			Q.push(A[s][j]);
			if (A[s][j] == t)
			{
				return 1;
			}
		}
	}
	return 0;
}

int main()
{
	cin >> n >> m;
	for (int i = 0; i < m; i++)
	{
		int s, t;
		cin >> s >> t;
		A[s].push_back(t);
	}
	cin >> q;
	for (int i = 0; i < q; i++)
	{
		int flag = 0;
		int s, t;
		cin >> s >> t;
		if (Find(s, t))
			cout << "yes" << endl;
		else if (Find(t, s))
			cout << "yes" << endl;
		else
			cout << "no" << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <iomanip> // << fixed << setprecision(xxx)
#include <algorithm> // do { } while ( next_permutation(A, A+xxx) ) ;
#include <vector>
#include <string> // to_string(nnn) // substr(m, n) // stoi(nnn)
#include <complex>
#include <tuple> // get<n>(xxx)
#include <queue>
#include <stack>
#include <map> // if (M.find(key) != M.end()) { }
#include <set> // S.insert(M);
// if (S.find(key) != S.end()) { }
// for (auto it=S.begin(); it != S.end(); it++) { }
// auto it = S.lower_bound(M);
#include <random> // random_device rd; mt19937 mt(rd());
#include <cctype>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstdlib> // atoi(xxx)
using namespace std;

#define DEBUG 0 // change 0 -> 1 if we need debug.
// insert #if<tab> by my emacs. #if DEBUG == 1 ... #end

typedef long long ll;

// const int dx[4] = {1, 0, -1, 0};
// const int dy[4] = {0, 1, 0, -1};

// const int C = 1e6+10;
// const ll M = 1000000007;

class Edge {
public:
  int src, dst, cost;
  Edge(int s, int d, int c)
    : src(s), dst(d), cost(c) {}
  friend bool operator<(const Edge& x, const Edge& y) {
    return x.cost < y.cost;
  }
};

typedef Edge State;

class Graph {
public:
  int N;
  vector<Edge>* V;
  // dfs, bfs
  int* visited;
  int* from;
  int time;
  int* time_d;
  int* time_f; // dfs
  int* dist;
  int* root;

  Graph(int n)
    : N(n), time(0) {
    V = new vector<Edge>[N];
    from = new int[N];
    time_d = new int[N];
    time_f = new int[N];
    visited = new int[N];
    fill(visited, visited+N, 0);
    dist = new int[N];
    root = new int[N];
  }
  ~Graph() {
    delete[] V;
    delete[] from;
    delete[] time_d;
    delete[] time_f;
    delete[] visited;
    delete[] dist;
    delete[] root;
  }

  void add_edge(int src, int dst, int cost = 1) {
    V[src].push_back(Edge(src, dst, cost));
  }

  bool is_same_root(int s, int t) {
    if (visited[s] == 0) {
      dfs(s);
    }
    if (visited[t] == 0) {
      dfs(t);
    }
    return (root[s] == root[t]);
  }

  void dfs(int start) {
    stack<State> S;
    S.push(State(-1, start, 0));
    while (!S.empty()) {
      State s = S.top();
      S.pop();
      if (visited[s.dst] == 0) {
        visited[s.dst] = 1;
        time_d[s.dst] = time++;
        from[s.dst] = s.src;
        dist[s.dst] = s.cost;
        root[s.dst] = start;
        S.push(s);
        for (auto x : V[s.dst]) {
          if (visited[x.dst] == 0) {
            S.push(State(s.dst, x.dst, s.cost + x.cost));
          }
        }
      } else if (visited[s.dst] == 1) {
        visited[s.dst] = 2;
        time_f[s.dst] = time++;
      }
    }
  }

  void bfs(vector<int> start) {
    assert(!start.empty());
    queue<State> Q;
    for (auto x : start) {
      Q.push(State(-1, x, 0));
    }
    while (!Q.empty()) {
      State s = Q.front();
      Q.pop();
      if (visited[s.dst] == 0) {
        visited[s.dst] = 1;
        time_d[s.dst] = time++;
        from[s.dst] = s.src;
        dist[s.dst] = s.cost;
        root[s.dst] = start[0];
        for (auto x : V[s.dst]) {
          if (visited[x.dst] == 0) {
            Q.push(State(s.dst, x.dst, s.cost + x.cost));
          }
        }
      }
    }
  }  
};

int main () {
  int n, m;
  cin >> n >> m;
  Graph g(n);
  for (auto i = 0; i < m; ++i) {
    int a, b;
    cin >> a >> b;
    g.add_edge(a, b);
    g.add_edge(b, a);
  }
  int q;
  cin >> q;
  for (auto i = 0; i < q; ++i) {
    int s, t;
    cin >> s >> t;
    cout << (g.is_same_root(s, t) ? "yes" : "no") << endl;
  }
}