Reduce/inject for accumulation in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sum all numbers in the array using inject.

Ruby

numbers = [1, 2, 3, 4]
total = numbers.[1](0) { |sum, n| sum + n }
puts total

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

Ainject

Breduce

Cmap

Dselect

Attempts:

3 left

💡 Hint

Common Mistakes

Using map instead of inject, which returns an array instead of a single value.

Using select, which filters elements but does not accumulate.

The inject method is used to accumulate a value by applying the block to each element. Here, it sums all numbers starting from 0.

2fill in blank

medium

Complete the code to multiply all numbers in the array using reduce.

Ruby

numbers = [2, 3, 4]
product = numbers.[1](1) { |prod, n| prod * n }
puts product

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

Ainject

Bmap

Creduce

Deach

Attempts:

3 left

💡 Hint

Common Mistakes

Using map which returns an array instead of a single value.

Using each which returns the original array.

The reduce method multiplies all numbers starting from 1, accumulating the product.

3fill in blank

hard

Fix the error in the code to correctly sum the lengths of all words.

Ruby

words = ["apple", "banana", "cherry"]
total_length = words.inject(0) { |sum, word| sum + word.[1] }
puts total_length

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Alength

Bcount

Csize

Dlength()

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() with parentheses which is valid but less idiomatic.

Using count which counts elements matching a condition, not length.

The length method returns the number of characters in a string. It is used here to sum all word lengths.

4fill in blank

hard

Fill both blanks to create a hash mapping words longer than 5 characters to their lengths.

Ruby

words = ["apple", "banana", "cherry", "date"]
lengths = words.inject({}) { |h, word| (word.[1] [2] 5) ? h.update(word => word.[1]) : h }
puts lengths

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Alength

Bsize

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' which selects shorter words.

Using size instead of length, which is acceptable but less common.

The code creates a hash with words as keys and their lengths as values, but only for words longer than 5 characters.

5fill in blank

hard

Fill all three blanks to create a hash with uppercase words as keys and original words as values if length greater than 4.

Ruby

words = ["pear", "peach", "plum", "pineapple"]
result = words.inject({}) { |h, word| (word.length [3] 4) ? h.update([1] => [2]) : h }
puts result

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

Aword.upcase

Bword

C>

Dword.length

Attempts:

3 left

💡 Hint

Common Mistakes

Using word.length as key instead of value.

Using '<' instead of '>' in the condition.

The hash keys are uppercase words, values are original words, filtered by length greater than 4.