Bonus — Collections Practice

Objectives

1. Become proficient at manipulating arrays
2. Practice using higher level Ruby enumerators like .collect and .sort

Instructions

The goal of this lab is to become proficient at manipulating arrays. Try experimenting with the built in Ruby methods as well as implementing your own logic to solve these. Write methods that solve each of the rspec tests.

Question 1: #sort_array_asc

Build a method sort_array_asc that takes in an array of integers and returns a copy of the array with the integers in ascending order.

Question 2: #sort_array_desc

Build a method sort_array_desc that takes in an array of integers and returns a copy of the array with the integers in descending order. Remember that .sort takes a block in which you can specify how you want your array sorted.

Question 3: #sort_array_char_count

Build a method sort_array_char_count that takes in an array of strings and returns a copy of the array with the strings ordered in ascending order by length. Remember that .sort takes a block in which you can specify how you want your array sorted.

Question 4: #swap_elements

Build a method swap_elements that takes in an array and swaps the second and third elements. Remember that array indices start at 0, so the second element has an index of 1 and the third element has an index of 2.

Advanced: Try building a method swap_elements_from_to that takes in three arguments, array, index, destination_index, that will allow you to specify the index of the element you would like to move to a new index. So:

swap_elements_from_to(["a", "b", "c"],0,2) #=> ["c", "b", "a"]
swap_elements_from_to(["a", "b", "c"],2,1) #=> ["a", "c", "b"]

Advanced #2: Try writing test coverage for it!

Question 5: #reverse_array

Build a method reverse_array that takes in an array of integers and returns a copy of the array with the elements in reverse order.

Question 6: #kesha_maker

Build a method called kesha_maker that takes in an array of strings and replaces the third character in each string with a $ ("dollar sign")—Ke$ha style. Use the .each method to iterate and build a new array to return at the end of your method, just like we did in the "My Each" lab.

Question 7: #find_a

Build a method find_a that returns all the strings in the array passed to it that start_with? (hint) the letter "a". You'll want to use a high level iterator for this that finds, selects, or detects elements based on a condition.

Question 8: #sum_array

Build a method sum_array that adds together all of the integers in the array and returns their sum.

Advanced: Try using the .inject method here.

Question 9: #add_s

Build a method that adds an "s" to each word in the array except for the second element in the array ("feet" is already plural).

Advanced: Iterators in Ruby are chainable, see if you can use .each_with_index in addition to .collect to solve this one in an elegant way. What happens if you write:

[1,2].each_with_index.collect{|element, index| }

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