How to resolve the algorithm Look-and-say sequence step by step in the Smalltalk programming language

Published on 12 May 2024 09:40 PM
#Smalltalk

How to resolve the algorithm Look-and-say sequence step by step in the Smalltalk programming language

Table of Contents

Problem Statement

The   Look and say sequence   is a recursively defined sequence of numbers studied most notably by   John Conway.

The   look-and-say sequence   is also known as the   Morris Number Sequence,   after cryptographer Robert Morris,   and the puzzle   What is the next number in the sequence 1,   11,   21,   1211,   111221?   is sometimes referred to as the Cuckoo's Egg,   from a description of Morris in Clifford Stoll's book   The Cuckoo's Egg.

Sequence Definition

An example:

Write a program to generate successive members of the look-and-say sequence.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Look-and-say sequence step by step in the Smalltalk programming language

Source code in the smalltalk programming language

String extend [
  lookAndSay [ |anElement nextElement counter coll newColl|
     coll := (self asOrderedCollection).
     newColl := OrderedCollection new.
     counter := 0.
     anElement := (coll first).
     [ coll size > 0 ]
     whileTrue: [
        nextElement := coll removeFirst.
	( anElement == nextElement ) ifTrue: [
           counter := counter + 1.
        ] ifFalse: [
	  newColl add: (counter displayString).
	  newColl add: (anElement asString).
	  anElement := nextElement.
	  counter := 1.
        ]
     ].
     newColl add: (counter displayString).
     newColl add: (anElement asString).
     ^(newColl join)
  ]
].

|r|
r := '1'.
10 timesRepeat: [
  r displayNl.
  r := r lookAndSay.
]

String compile:
  'lookAndSay |anElement nextElement counter coll newColl|
     coll := (self asOrderedCollection).
     newColl := OrderedCollection new.
     counter := 0.
     anElement := (coll first).
     [ coll size > 0 ]
     whileTrue: [
        nextElement := coll removeFirst.
	( anElement == nextElement ) ifTrue: [
           counter := counter + 1.
        ] ifFalse: [
	  newColl add: (counter displayString).
	  newColl add: (anElement asString).
	  anElement := nextElement.
	  counter := 1.
        ]
     ].
     newColl add: (counter displayString).
     newColl add: (anElement asString).
     ^('''' join: newColl)'
  classified: 'toys'.
 
result := OrderedCollection new.
r := '1'.
result add: r.
result addAll: ((1 to: 10) collect: [ :i |
  r := r lookAndSay.
]).
result.

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