Another Chris Pine Tutorial Question

Let’s write a program which asks us to type in as many words as we
want (one word per line, continuing until we just press Enter on an
empty line), and which then repeats the words back to us in
alphabetical order. OK?

So… first we’ll—uh… um… hmmm… Well, we could—er… um…

You know, I don’t think we can do it. We need a way to store an
unknown amount of words, and how to keep track of them all together,
so they don’t get mixed up with other variables. We need to put them
in some sort of a list. We need arrays.
puts “Let’s make a shopping list!”

shoplist = []

while shoplist.last != ‘’

shoplist.push(gets.downcase.chomp)

end

shoplist.pop

puts shoplist.sort

The program asks for one word per line but there is no way one can do
that utilizing the methods the tutorial has expounded upon up to this
point so I settled for what I got here.

However, it asks you to then do this:

• Try writing the above program without using the sort method. A large
part of programming is solving problems, so get all the practice you
can!

Could somebody point me in the right direction, or give me an example
of how that would be possible? I’m racking my brain but I can not
think of a way to do it without using methods and tools that you are
not yet supposed to use at this point in the tutorial (i.e. regex)

Have you already been introduced to String#<=> [
http://ruby-doc.org/core/classes/String.html#M000778 ] ? You could use
it as
the basis for comparing each of the input strings to all others that
you’ve
collected so far. How’s that for a push in one direction?

Regards,
Craig

danielj wrote:

in some sort of a list. We need arrays.
shoplist.pop
• Try writing the above program without using the sort method. A large
part of programming is solving problems, so get all the practice you
can!

Could somebody point me in the right direction, or give me an example
of how that would be possible? I’m racking my brain but I can not
think of a way to do it without using methods and tools that you are
not yet supposed to use at this point in the tutorial (i.e. regex)

There’s not really any point to limiting yourself. Whatever you come up
with will essentially be a crude or simplified sorting algorithm. If
you really didn’t want to use the sort method, you could do something
like this:

words = []
while true
word = gets.chomp
break if word == ‘’
words << word
end

while words.size > 0
word = words.min{|a,b| a.downcase <=> b.downcase }
puts word
words -= [word]
end

However, what you’ve ended up doing is creating something a lot like a
selection sort only instead of swapping with the front of the list
you’re printing it and removing it from the list. In effect, it’s just
a really inefficient version of sort.

Maybe you’ve taken this as a personal challenge, but I’ve come to except
some (most?) texts have at least some little quirks like this. They’re
best ignored while you move on to more interesting things. If you want
a challenge, there’s a huge backlog of RubyQuiz problems that are much
more interesting.

On 30.08.2008 22:55, danielj wrote:

However, it asks you to then do this:

• Try writing the above program without using the sort method. A large
part of programming is solving problems, so get all the practice you
can!

Could somebody point me in the right direction, or give me an example
of how that would be possible? I’m racking my brain but I can not
think of a way to do it without using methods and tools that you are
not yet supposed to use at this point in the tutorial (i.e. regex)

The trick I assume Chris is targeting at is to insert words at the
correct position. That way your list is always sorted and you do not
need an explicit sort operation.

Kind regards

robert

On 2008-08-31 13:00:33 +0100, Robert K. [email protected]
said:

The trick I assume Chris is targeting at is to insert words at the
correct position. That way your list is always sorted and you do not
need an explicit sort operation.

That’s a good idea. Or I suppose you could implement your own sorting
method and call that instead.

On Aug 31, 11:21 pm, timr [email protected] wrote:

shoplist.push(gets.downcase.chomp)

However, it asks you to then do this:

• Try writing the above program without using the sort method. A large
part of programming is solving problems, so get all the practice you
can!

Could somebody point me in the right direction, or give me an example
of how that would be possible? I’m racking my brain but I can not
think of a way to do it without using methods and tools that you are
not yet supposed to use at this point in the tutorial (i.e. regex)

SORRY. AFTER FIXING THE COMMENTS TO BE MORE READABLE–

On Aug 30, 1:55 pm, danielj [email protected] wrote:

in some sort of a list. We need arrays.
shoplist.pop
part of programming is solving problems, so get all the practice you
can!

Could somebody point me in the right direction, or give me an example
of how that would be possible? I’m racking my brain but I can not
think of a way to do it without using methods and tools that you are
not yet supposed to use at this point in the tutorial (i.e. regex)

words = []
loop do #loop allows one to do an indefinite amount
of something–must set an exit
#inside of the loop.
incoming = gets
if incoming == “\n” then #if a blank line is entered, we are done.
Sort and puts the list.
puts words.sort
exit
else
words << incoming #if data is entered, add it to the array of
words.
end
end

#=>
alphabet soup
bananas
coca cola
hot dogs
kool aid
lettuce
milk
potatoes
spinach
sugar

Tim Rand

words = []
loop do #loop allows one to do an indefinite amount
# of something–must set an exit
#inside of the loop.
incoming = gets
if incoming == “\n” then #if a blank line is entered, we are done.
#Sort and puts the list.
puts words.sort
exit
else
words << incoming #if data is entered, add it to the array of
words.
end
end

#=>
alphabet soup
bananas
coca cola
hot dogs
kool aid
lettuce
milk
potatoes
spinach
sugar

Tim Rand

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