Flat_map for nested flattening in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to flatten the nested arrays using flat_map.

Ruby

nested = [[1, 2], [3, 4], [5, 6]]
flat = nested.[1] { |arr| arr }
puts flat.inspect

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

Aselect

Bflat_map

Ceach

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'map' only returns nested arrays without flattening.

Using 'each' does not return a new array.

Using 'select' filters elements but does not flatten.

The flat_map method maps and flattens one level of nested arrays, producing a single flat array.

2fill in blank

medium

Complete the code to flatten and double each number in the nested arrays.

Ruby

nested = [[1, 2], [3, 4], [5, 6]]
result = nested.[1] { |arr| arr.map { |n| n * 2 } }
puts result.inspect

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

Aflat_map

Bmap

Ceach

Dselect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'map' results in nested arrays after doubling.

Using 'each' does not return a new array.

Using 'select' filters elements but does not transform or flatten.

flat_map applies the block to each sub-array, then flattens the result into a single array.

3fill in blank

hard

Fix the error in the code to flatten nested arrays of strings into a single array of characters.

Ruby

words = [["hi", "there"], ["ruby", "code"]]
chars = words.[1] { |word_arr| word_arr.map(&:chars) }
puts chars.flatten.inspect

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

Aflat_map

Bmap

Ceach

Dselect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'map' returns nested arrays requiring extra flattening.

Using 'each' does not return a new array.

Using 'select' filters but does not flatten.

Using flat_map here flattens one level after mapping, so you don't need to call flatten separately.

4fill in blank

hard

Fill both blanks to flatten and convert nested arrays of numbers to strings.

Ruby

nested = [[1, 2], [3, 4], [5, 6]]
result = nested.[1] { |arr| arr.[2](&:to_s) }
puts result.inspect

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

Aflat_map

Bmap

Ceach

Dselect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'map' instead of 'flat_map' on the outer array keeps nesting.

Using 'each' instead of 'map' inside does not transform elements.

flat_map flattens the outer array after mapping, and map converts each number to a string.

5fill in blank

hard

Fill all three blanks to flatten nested arrays and select only even numbers as strings.

Ruby

nested = [[1, 2], [3, 4], [5, 6]]
result = nested.[1] { |arr| arr.[2] { |n| n.[3] }}
puts result.inspect

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

Aflat_map

Bselect

Ceven?

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'map' instead of 'flat_map' keeps nested arrays.

Using 'map' instead of 'select' filters incorrectly.

Using wrong condition instead of 'even?'.

flat_map flattens the array, select filters even numbers, and even? checks if a number is even.