Problem:
Book Index

Books are indexed. Write a program which reads a list of pairs of a word and a page number, and prints the word and a list of the corresponding page numbers.

You can assume that a word consists of at most 30 characters, and the page number is less than or equal to 1000. The number of pairs of a word and a page number is less than or equal to 100. A word never appear in a page more than once.

The words should be printed in alphabetical order and the page numbers should be printed in ascending order.

Input

word page_number
:
:

Output

word
a_list_of_the_page_number
word
a_list_of_the_Page_number
:
:

Sample Input

style 12
even 25
introduction 3
easy 9
style 7
document 13
style 21
even 18

Output for the Sample Input

document
13
easy
9
even
18 25
introduction
3
style
7 12 21

Solution in Scala (judge verdict: Accepted)

object Main extends App {
  val src: List[(String, Array[Int])] = io.Source.stdin.getLines.toList.map(_.split(" ")).map { case Array(a, b) => (a, Array(b)) }.sortWith(_._1 < _._1).map( tup => (tup._1, tup._2.map(_.toInt)))

  def step(li: List[(String, Array[Int])], tup: (String, Array[Int])): List[(String, Array[Int])] = li match {
    case Nil => List(tup)
    case h :: tail if h._1 == tup._1 => (h._1, h._2 :+ tup._2(0)) :: tail
    case h :: tail => h :: step(tail, tup)
  }

  val mergeNum: List[(String, Array[Int])] = (Nil /:[List[(String, Array[Int])]] src)(step)

  mergeNum.map { case (str, arr) => println(s"${str}\n${arr.sorted.mkString(" ")}")}
}