ReverseWords

Welcome to the reverse_words gem!

This gem adds String#reverse_words and String#reverse_words! to the core Ruby String class.

String#reverse_words: returns a copy of the receiving string object, in which all words in the sentence are reversed.
String#reverse_words!: like String#reverse_words, but returns nil and modifies the receiving string object instead.

Installation

Add this line to your application's Gemfile:

gem 'reverse_words'

And then execute:

$ bundle

Or install it yourself as:

$ gem install reverse_words

Usage

$ bin/console
irb(main):001:0> "the big black cat.".reverse_words
=> "cat black big the."
irb(main):002:0> str = "hello world!"
=> "hello world!"
irb(main):003:0> str.reverse_words!
=> nil
irb(main):004:0> str
=> "world hello!"

Notes

Time and Space Complexity

Time complexity of the algorithm is O(n), where n is the number of characters in the input string.

The space complexity (while also still O(n)) is unfortunately not optimal, as there are approaches that can work "in place" without copying the string to reverse. See here for an example implementation of such an algorithm in C/C++.

Handling Blanks, Punctuation, and Capitalization

When the words in the input sentence are reversed, all trailing and leading blanks are removed from the input string. The same holds true for duplicate spaces around the words in the input string. I.e.,

> " this is   a  thing that has   blanks ".reverse_words
=> "blanks has that thing a is this"

I decided to handle punctuation such that input strings that end in any sequence of ., !, or ?s would remain at the end of the sentence with the reversed word order. I.e.,

> "english has interrobangs!?".reverse_words
=> "interrobangs has english!?"

I decided not to address adapting capitalization, though. I.e.:

> "Hello world".reverse_words
=> "world Hello"

Development

After checking out the repo, run bin/setup to install dependencies.

Then, run bundle exec rake spec to run the tests.

You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install.

timbogit / reverse_words