Manipulating Strings and Arrays in Ruby

Question

I've got:

@fruit = ["Apples, Oranges, Bananas", "Apples", "Bananas, Pears", "Bananas, Apples, Pears", "Pears"]

I want to do two different things with this, first turn it into a pure array with only one instance of each:

["Apples", "Oranges", "Bananas", "Pears"]

Secondly I want to be able to determine how many of a given instance there are in the array:

@fruit.count("Apples") = 3

Thirdly, is it possible to order the array by the number of instances:

@fruit.sort = ["Apples", "Apples", "Apples", "Bananas", "Bananas", "Bananas", "Pears", "Pears", "Pears", "Oranges"]

What array/string functions would I have to use to do this?

Jimmy · Accepted Answer · 2011-10-02 20:05:00Z

6

arr = ["Apples, Oranges, Bananas", "Apples", "Bananas, Pears", "Bananas, Apples, Pears", "Pears"]

hsh = Hash.new { |h, k| h[k] = 0 }

arr.each do |str|
  fruits = str.split(/, /)
  fruits.each do |fruit|
    hsh[fruit] += 1
  end
end

p hsh.keys
# => ["Apples", "Oranges", "Bananas", "Pears"]

hsh.keys.each { |fruit| puts "#{fruit}: #{hsh[fruit]}" }
# => Apples: 3
# => Oranges: 1
# => Bananas: 3
# => Pears: 3

answered Oct 2, 2011 at 20:05

Jimmy

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2 Comments

Marian Theisen Over a year ago

first of all, this shows a great and underused feature of Hash.new -> +1. and second, this saves you some loops. remember that each enumerator method: map, flatten, uniq and count all take at least 1 iteration over your array.

tokland Over a year ago

@marian: don't worry about performance too soon. Functional constructions (map/select/flatten) promote good code, while loops using custom imperative eachs are harder to understand.

fl00r · Accepted Answer · 2011-10-02 20:26:52Z

4

@fruit = ["Apples, Oranges, Bananas", "Apples", "Bananas, Pears", "Bananas, Apples, Pears", "Pears"]

@fruits = @fruit.map{|f| f.split(", ")}.flatten
#=>["Apples", "Oranges", "Bananas", "Apples", "Bananas", "Pears", "Bananas", "Apples", "Pears", "Pears"]
@fruits.uniq
#=> ["Apples", "Oranges", "Bananas", "Pears"]
@fruits.count{|f| f=="Apples"}
#=>3

edited Oct 2, 2011 at 20:26

answered Oct 2, 2011 at 20:03

fl00r

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1 Comment

goddamnyouryan Over a year ago

perfect! Flatten, that's what I didn't know! Thanks.

Tilo · Accepted Answer · 2011-10-02 20:46:07Z

2

A hash is the better data structure to do this:

@fruit = ["Apples, Oranges, Bananas", "Apples", "Bananas, Pears", "Bananas, Apples, Pears", "Pears"]

h = Hash.new

@fruit.each do |str|
  str.split(/,/).each do |f|
    f.strip!
    h[f] ||= 0
    h[f] += 1
  end
end


h.keys
 => ["Apples", "Oranges", "Bananas", "Pears"] 

h
 => {"Apples"=>3, "Oranges"=>1, "Bananas"=>3, "Pears"=>3} 

h["Apples"]
 => 3

you can then process the accumulated data in the hash to print out a sorted array if you need one.

edited Oct 2, 2011 at 20:46

answered Oct 2, 2011 at 20:36

Tilo

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Comments

derp · Accepted Answer · 2011-10-02 20:10:28Z

0

@fruit = ["Apples, Oranges, Bananas", "Apples", "Bananas, Pears", "Bananas, Apples, Pears", "Pears"]

p @fruit.map{|f| f.split(', ') }.flatten.uniq
#=> ["Apples", "Oranges", "Bananas", "Pears"]

p @fruit.count{|f| f.include?("Apples")}
#=> 3

answered Oct 2, 2011 at 20:10

derp

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