Ruby Challenge: Create a word occurrence counter

TL; DR: Get the solution on my Github repository.

Problem

Create a word occurrence counter.

Given a sentence, such as the following one:

sentence = "I love Ruby, Ruby is a great language!"

The result would be a hash

{"I"=>1, "love"=>1, "Ruby,"=>2, "is"=>1, "a"=>1, "great"=>1, "language!"=>1}

Steps

Let's build our solution one step at a time, so, you can grasp it.

Basically, there are 3 steps:

Store the result;
Match words;
Count the words.

Store the result

Let's start by creating a Hash object. This object is our counter.

def count_word_occurrences(sentence)
  word_counter = Hash.new(0)

  return word_counter
end

Match each word

In this step, we're going to identify and separate each word.

Scan method

In order to achieve this, we're going to use the scan method. Take a look at the following approach:

sentence.scan(/\w+/)

Usage

The previous code snippet uses the scan method. This method is provided by the Ruby's String class. It is used to search a string (sentence in this case) for all occurrences of a specified pattern and returns an array of all matches found.

In the given code snippet, the pattern specified is /\w+/.

Regular expression pattern

\w is a metacharacter that matches any word character, which includes alphabetic characters (both uppercase and lowercase) and digits. It is equivalent to the character class [A-Za-z0-9_].

The plus sign + is a quantifier that specifies that the preceding pattern (\w in this case) should be matched one or more times consecutively. Therefore, /\w+/ matches one or more consecutive word characters.

Return

The scan method scans the sentence string and finds all occurrences of the pattern /\w+/. It then returns an array containing all the words found in the sentence.

Result

sentence = "I love Ruby, Ruby is a great language!"

def count_word_occurrences(sentence)
  word_counter = Hash.new(0)

  # Use regular expression to match each word in the sentence
  @words = sentence.scan(/\w+/)

  word_counter
end

count_word_occurrences(sentence)
puts @words

Since we're using the scan method, the previous code would result in an array:

["I", "love", "Ruby", "Ruby", "is", "a", "great", "language"]

Output

Count the words

As we already checked, by using the scan method, we got an array of words.

Now, we need to iterate through this array and check if the word element is repeated, cause if it is, we're going to add one to the world_counter variable:

words.each do |word|
    word_counter[word] += 1
  end

The previous code is our cornerstone. Every iteration is going to add a key value to the word_counter

word_counter[word]

And add 1 to the word_counter if the word is repeated:

word_counter[word] += 1

Complete solution

Code

sentence = "I love Ruby, Ruby is a great language!"

def count_word_occurrences(sentence)
  word_counter = Hash.new(0)

  words = sentence.scan(/\w+/)

  words.each do |word|
    word_counter[word] += 1
  end

  word_counter
end

puts count_word_occurrences(sentence)

Github repository

Take a look at it here.

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Final thoughts

I hope this article helped you. Let me know if you have any questions.

Your thoughts, suggestions and corrections are more than welcome.

By the way, feel free to drop your suggestions on new blog articles.

Hope to see you next time.

Ruby Challenge: Create a word occurrence counter

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Problem

Steps

Store the result

Match each word

Scan method

Usage

Regular expression pattern

Return

Result

Count the words

Complete solution

Code

Github repository

Be happy

Let's get to know each other

Final thoughts

Command Palette

Comments

Ruby

Leetcode 217. Contains Duplicate - Solution in Ruby

More from this blog

Problem

Steps

Store the result

Match each word

Scan method

Usage

Regular expression pattern

Return

Result

Count the words

Complete solution

Code

Github repository

Be happy

Let's get to know each other

Final thoughts