[Solved] What is the output of the following Ruby code? arr = [[1, 2], [3, 4]] result = arr.flat_map { |sub| sub.map { |x| x * 2 } } puts result.inspect | Ruby

Ruby - Enumerable and Collection Processing

What is the output of the following Ruby code?

arr = [[1, 2], [3, 4]]
result = arr.flat_map { |sub| sub.map { |x| x * 2 } }
puts result.inspect

A[2, 4, 6, 8]

B[[2, 4], [6, 8]]

C[1, 2, 3, 4]

D[[1, 2], [3, 4]]

Step-by-Step Solution

Solution:

Step 1: Inner map doubles each element
For each sub-array, sub.map { |x| x * 2 } creates a new array with doubled values: [2,4] and [6,8].
Step 2: flat_map flattens one level
flat_map combines these arrays into a single flat array: [2, 4, 6, 8].
Final Answer:
[2, 4, 6, 8] -> Option A
Quick Check:
flat_map flattens mapped arrays one level [OK]

Quick Trick: flat_map flattens one level after mapping [OK]

Common Mistakes:

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