Group_by for categorization in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to group numbers by their parity (even or odd).

Ruby

numbers = [1, 2, 3, 4, 5]
groups = numbers.group_by { |n| n.[1] }
puts groups

Drag options to blanks, or click blank then click option'

Ato_s

Bodd?

Cabs

Deven?

Attempts:

3 left

💡 Hint

Common Mistakes

Using odd? groups by odd numbers, which is not what the question asks.

Using to_s or abs does not categorize by parity.

The even? method returns true for even numbers, so grouping by n.even? categorizes numbers into even and odd groups.

2fill in blank

medium

Complete the code to group words by their first letter.

Ruby

words = ['apple', 'banana', 'apricot', 'blueberry']
groups = words.group_by { |word| word.[1] }
puts groups

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Afirst

Blength

Cupcase

Dreverse

Attempts:

3 left

💡 Hint

Common Mistakes

Using length groups by word length, not first letter.

Using upcase returns the whole word in uppercase, not the first letter.

The first method returns the first character of a string, so grouping by word.first groups words by their first letter.

3fill in blank

hard

Fix the error in the code to group numbers by their remainder when divided by 3.

Ruby

numbers = [1, 2, 3, 4, 5, 6]
groups = numbers.group_by { |n| n [1] 3 }
puts groups

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A/

B%

C*

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using / divides numbers but does not give remainder.

Using * or - does not relate to remainder.

The modulo operator % gives the remainder of division, so n % 3 groups numbers by their remainder when divided by 3.

4fill in blank

hard

Fill both blanks to group words by their length and select only words longer than 3 letters.

Ruby

words = ['cat', 'dog', 'elephant', 'bee', 'ant']
groups = words.group_by { |word| word.[1] }
filtered = groups.select { |length, words| length [2] 3 }
puts filtered

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Alength

B>

C<

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using size is also valid for length but only one correct answer is accepted here.

Using < selects shorter words, not longer.

Grouping by word.length groups words by their length. Selecting where length is greater than 3 filters only longer words.

5fill in blank

hard

Fill all three blanks to group numbers by their sign and select only positive numbers.

Ruby

numbers = [-2, -1, 0, 1, 2]
groups = numbers.group_by { |n| n.[1] }
positive = groups.select { |sign, nums| sign == [2] }
puts positive[[3]]

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Anegative?

Btrue

Cfalse

Dpositive?

Attempts:

3 left

💡 Hint

Common Mistakes

Using negative? groups negative numbers, not positive.

Using false selects non-positive numbers.

The positive? method returns true for positive numbers. Selecting groups where sign is true filters positive numbers. Accessing positive[true] gets the array of positive numbers.