Problem:
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Connected Components

Write a program which reads relations in a SNS (Social Network Service), and judges that given pairs of users are reachable each other through the network.

Input

In the first line, two integer $n$ and $m$ are given. $n$ is the number of users in the SNS and $m$ is the number of relations in the SNS. The users in the SNS are identified by IDs $0, 1, ..., n-1$.

In the following $m$ lines, the relations are given. Each relation is given by two integers $s$ and $t$ that represents $s$ and $t$ are friends (and reachable each other).

In the next line, the number of queries $q$ is given. In the following $q$ lines, $q$ queries are given respectively. Each query consists of two integers $s$ and $t$ separated by a space character.

Output

For each query, print "yes" if $t$ is reachable from $s$ through the social network, "no" otherwise.

Constraints

$2 \leq n \leq 100,000$

$0 \leq m \leq 100,000$

$1 \leq q \leq 10,000$

Sample Input

10 9
0 1
0 2
3 4
5 7
5 6
6 7
6 8
7 8
8 9
3
0 1
5 9
1 3

Sample Output

yes
yes
no

Solution in Scala (judge verdict: WA: Presentation Error)

import scala.collection.mutable.ArrayBuffer
import scala.io.StdIn

object Main extends App {

  val Array(n, m) = StdIn.readLine().split(' ').map(_.toInt)
  val groupIndex = Array.fill[Int](n)(-1)
  val friends = Array.ofDim[ArrayBuffer[Int]](n)
  
  (0 until m).foreach { _ =>
    val a = StdIn.readLine().split(' ').map(_.toInt)
    friends(a(0)) = if(friends(a(0)) == null) ArrayBuffer.empty[Int] else friends(a(0))
    friends(a(0)) += a(1)
    friends(a(1)) = if(friends(a(1)) == null) ArrayBuffer.empty[Int] else friends(a(1))
    friends(a(1)) += a(0)
  }

  def dps(r: Int, groupIdx: Int): Unit = {
    var buff = ArrayBuffer.empty[Int]
    buff += r
    groupIndex(r) = groupIdx
    while(buff.nonEmpty){
      val u = buff.head
      buff = buff.tail
      friends(u).foreach{ v =>
        if(groupIndex(v) == -1){
          groupIndex(v) = groupIdx
          buff += v
        }
      }
    }
  }

  var idx = 1
  (0 until n).foreach { v =>
    if(groupIndex(v) == -1){
      dps(v, idx + 1)
      idx += 1
    }
  }

  val q = StdIn.readLine().toInt
  val sbbuff = new StringBuilder
  //println(s"q: $q")
  (0 until q).foreach { _ =>
    val ql = StdIn.readLine().split(' ').map(_.toInt)
    sbbuff.append(if(groupIndex(ql(0)) == groupIndex(ql(1))){
      f"yes%n" 
    } else {
      f"no%n"
    })
  }
  
  println(sbbuff.toString())
  
}