Day 1 of 30: Ruby Coding Challenge - Arrays and Blocks

Hey friend!

This is the first part of this series of 30 Coding Challenges in Ruby for:

• Folks who are just getting started.
• Folks who just want to stretch their brain a little bit.
• Folks who just want to have fun in preparing themselves for coding interviews.

What about the Ruby environment?

• No excuses, you don’t need that.
• Here is the link for a Ruby Online Compiler, which I’m going to share all of the code and you can also play around.
• It’s all about problem-solving skills and concepts, not about programming languages :).

The most important goal: It’s all about having fun while solving simple but great coding challenges.

I’m the Problem, Nice to Meet You

Given an array of numbers, we want to count how many items are greater than 5

C'mon, give us something more difficult and interesting!

I know, I know what you’re thinking, but this is just to start our journey together.

I’m going to break this down into 4 steps:

• Logic to solve the problem.
• Solving with a classic for loops.
• Organizing our code with methods.
• Bonus: Meeting Blocks in Ruby.

Are you ready? Let’s get into it : )

#1 Logic to Solve the Problem

Yes, the logic is pretty simple. Again, just to stretch our legs and arms to the run

• Given an array.
• Go through all of the numbers.
• For each number, you compare if the number is greater than 5.
• You increment a variable (let’s call it count).
• You print the variable count after going through the array.

#2 Classic For-Loop Expression

Again, don’t worry about the Ruby syntax. Focus on concepts and logic.

For the code below we’ve created a classic for-loop expression, and for each item in the given array, we’re checking if the number is greater than 5, just like the previous logic

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array = [15, 7, 3, 2, 17, 12, 1]

count = 0;

for item in array

  if item > 5

    count += 1

  end

end

puts count  # prints out the count value, which is 4. Nice

#3 Organizing With a Method

Nothing special here. Just organizing the kitchen with a method.

Notice that we’re taking a number as an argument, which will be the number used to compare the items in the array.

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def how_many_are_greater_than(number, array)

  count = 0;

  for item in array

    if item > number

      count += 1

    end

  end

  return count # in Ruby we don't need to use return btw

end

array = [15, 7 , 3, 2, 17, 12, 1]

count = how_many_are_greater_than(5, array) # a little bit better, isn't it?

puts count

Pretty simple, right?

What about doing that in a more Ruby(ish) way? 

#4 Hipster Time: Blocks in Ruby

Bonus hipster time.

Ruby (as many other languages) has its own way to do a few things and that is called Ruby Way or Rubyish Way to do things

An array in Ruby provides a method called count(), which receives a block that can be an expression to be evaluated

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array.count do |item|

  item > number

end

Notice that:

• item: is just a single item from our array. This block   magically   automatically executes a for loop expression
• item > number: is the expression to be evaluated for each item

The complete code:

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def how_many_are_greater_than_rubyish(number, array)

  array.count do |item|

    item > number

  end

end

array = [15, 7 , 3, 2, 17, 12, 1]

count = how_many_are_greater_than_rubyish(5, array)

puts count

But wait. Where is the count variable and how we return it? Brilliant question.

Ruby automatically increments an internal variable each time the expression item > number is evaluated to true and keeps the result in this internal variable.

When the execution is finished, Ruby automatically returns the result for us.

Don’t believe me? Check the code below:

def how_many_are_greater_than_rubyish(number, array)  

  return array.count do |item|

    item > number

  end

end

array = [15, 7 , 3, 2, 17, 12, 1]

count = how_many_are_greater_than_rubyish(5)

puts count

Now, I’m explicitly using the return keyword, which will behave in the same way, returning the final result after the expression being evaluated for each item in the array.

This is a more declarative approach than an imperative one, but this is a discussion for an upcoming article.

Well done, Ruby! 

That’s it. Thanks for your visit, really appreciate your time and see you soon :)

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