Hi,
I am new to programming and following Chris Pines book. There is an
exercise in the book to write a method similar to .sort that will
arrange an array of string in alphabetical order. I will paste the
exercise:
OK. So we want to sort an array of words, and we know how to find out
which of two words comes first in the dictionary (using <).
What strikes me as probably the easiest way to do this is to keep two
more lists around: one will be our list of already-sorted words, and
the
other will be our list of still-unsorted words. We’ll take our list of
words,
find the “smallest” word (that is, the word that would come first in
the
dictionary), and stick it at the end of the already-sorted list. All
of the
other words go into the still-unsorted list. Then you do the same
thing
again but using the still-unsorted list instead of your original list:
find
the smallest word, move it to the sorted list, and move the rest to
the
unsorted list. Keep going until your still-unsorted list is empty.
I think I covered the first bit of the exercise but when I try to
repeat my method recursively it fails.
Would you be please so kind to take a look at my code and tell me what
am I doing wrong?
puts 'Please enter a list of words you would like to arrange'
puts 'in alphabetical order:'
list_of_words = []
input = 'empty'
while input != ''
input = gets.chomp
if input != ''
list_of_words.push input
end
end
def arrange some_array
recursive_arrange some_array, []
end
def recursive_arrange unsorted_array, sorted_array
# Initializing the array "still_unsorted_array"
still_unsorted_array = []
# Finding the smallest word on the array "list_of_words"
smallest = unsorted_array [0]
unsorted_array.each do |word|
if smallest > word
smallest = word
end
end
# Adding the smallest word from the array of "unsorted words" to the
array of "sorted_words"
sorted_array.push smallest
# Adding the words from the array of "unsorted_array" to the array of
"still_unsorted_array"
# with the exception of the content of variable "smallest"
bigger = 'empty'
unsorted_array.each do |word|
if word != smallest
bigger = word
still_unsorted_array.push bigger
end
end
# Clearing the array of "unsorted_array" so it can be re-used
unsorted_array = []
# Adding the smallest word from the array of "still_unsorted words" to
the array of "sorted_words"
smallest = still_unsorted_array [0]
still_unsorted_array.each do |word|
if smallest > word
smallest = word
end
end
# Adding the smallest word from the array of "still_unsorted words" to
the array of "sorted_words"
sorted_array.push smallest
# Adding the remaining words from the array "still_unsorted_words" to
the array of
# "unsorted_words"
still_unsorted_array.each do |word|
if word != smallest
bigger = word
unsorted_array.push bigger
end
end
# This is the bit I tried to call the method recursively.
if unsorted_array == unsorted_array = []
puts sorted_array
else
recursive_arrange unsorted_array, sorted_array
end
puts 'unsorted array:'
puts unsorted_array
puts 'still unsorted array:'
puts still_unsorted_array
puts 'sorted array:'
puts sorted_array
end
arrange list_of_words
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