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 <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <stack>
#define rep(i, n) for(int i=0;i<n;i++)
#define NOT_FOUND 0
#define ENQUEUED 1
using namespace std;

vector<int> graph[100001];
int memo[100001];

int dfs(int start, int end) {
    if (start == end) {
        return 1;
    }
    memset(memo, NOT_FOUND, sizeof(memo));
    stack<int> stack;
    stack.push(start);
    memo[start] = ENQUEUED;
    int counter = 0;

    while(!stack.empty() && counter != 10) {
        counter += 1;
        int v = stack.top();
        stack.pop();
        vector<int> edges = graph[v];

        for (int i = 0; i < edges.size(); i++) {
            int next = edges[i];
            if (next == end) {
                return 1;
            }
            if (memo[next] == NOT_FOUND) {
                memo[next] = ENQUEUED;
                stack.push(next);
            }
        }
    }
    return 0;
}

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

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

    int q;
    cin >> q;

    for (int i = 0; i < q; i++) {
        int s, d;
        cin >> s >> d;
        if (dfs(s, d)) {
            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++);
  }
}

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<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<vector>
using namespace std;
vector<vector<int>> G(100000);
vector<int> c(100000);
void dfs(int s, int x){
    if(c[s]) return;
    c[s]=x;
    for(auto a:G[s]) dfs(a,x);
}
int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n,m;
    cin>>n>>m;
    for(int i=0;i<m;++i){
        int a,b;
        cin>>a>>b;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    for(int i=0;i<n;++i) dfs(i,i+1);
    int q;
    cin>>q;
    for(int i=0;i<q;++i){
        int a,b;
        cin>>a>>b;
        cout<<(c[a]-c[b]?"no":"yes")<<endl;
    }
}

C++: 
#include<stdio.h>
#include<queue>
#include<algorithm>

#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");
    }

}