Given a large array arr = (1..1000000).to_a, which Ruby code snippet efficiently finds the first 3 even numbers greater than 500000 using lazy enumerators?

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Ruby - Functional Patterns in Ruby

Given a large array arr = (1..1000000).to_a, which Ruby code snippet efficiently finds the first 3 even numbers greater than 500000 using lazy enumerators?

Aarr.lazy.select { |x| x > 500000 && x.even? }.first(3)

Barr.select { |x| x > 500000 && x.even? }.first(3)

Carr.lazy.map { |x| x * 2 }.first(3)

Darr.take(3).lazy.select(&:even?)

Step-by-Step Solution

Solution:

Step 1: Understand the goal and data size
We want the first 3 even numbers greater than 500,000 from a large array. Using lazy enumerators avoids processing the entire array.
Step 2: Analyze each option
arr.lazy.select { |x| x > 500000 && x.even? }.first(3) uses lazy, filters with select for the condition, then takes first 3 - efficient and correct.
arr.select { |x| x > 500000 && x.even? }.first(3) processes entire array eagerly, inefficient.
arr.lazy.map { |x| x * 2 }.first(3) maps all elements, not filtering by condition.
arr.take(3).lazy.select(&:even?) takes first 3 elements then filters, which misses numbers > 500,000.
Final Answer:
arr.lazy.select { |x| x > 500000 && x.even? }.first(3) -> Option A
Quick Check:
Lazy select with condition then first(3) = C [OK]

Quick Trick: Use lazy select with condition, then first(n) for efficiency [OK]

Common Mistakes:

Using eager select causing slow processing
Filtering after taking first 3 elements incorrectly
Using map instead of select for filtering

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Given a large array arr = (1..1000000).to_a, which Ruby code snippet efficiently finds the first 3 even numbers greater than 500000 using lazy enumerators?

Step 1: Understand the goal and data size

Step 2: Analyze each option

Final Answer:

Quick Check:

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