Each as the primary iterator in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of each with array iteration

What is the output of this Ruby code?

Ruby

arr = [1, 2, 3]
result = []
arr.each do |x|
  result << x * 2
end
puts result.inspect

A [2, 4, 6]

B [1, 2, 3]

C nil

D [3, 6, 9]

💡 Hint

Remember that each goes through every element and you can collect results in another array.

The each method goes through each element in arr. For each element x, it multiplies by 2 and adds to result. So result becomes [2, 4, 6].

❓ Predict Output

intermediate

Each with hash iteration output

What will this Ruby code print?

Ruby

h = {a: 1, b: 2}
h.each do |key, value|
  puts "#{key}:#{value * 3}"
end

A

a:3
b:2

B

a:1
b:2

C

a:1
b:6

D

a:3
b:6

💡 Hint

Each goes through each key-value pair. Value is multiplied by 3 in the output.

The each method iterates over each key-value pair. For each, it prints key and value multiplied by 3. So a:3 and b:6 are printed.

🔧 Debug

advanced

Why does this each loop not modify the array?

Look at this Ruby code. Why does the array stay the same after the each loop?

Ruby

arr = [1, 2, 3]
arr.each do |x|
  x = x * 10
end
puts arr.inspect

A Because x is a copy of each element, modifying x does not change the array elements.

B Because each does not run the block at all.

C Because x is a reference to the array element and changes should reflect.

D Because the array is frozen and cannot be changed.

💡 Hint

Think about whether changing the block variable changes the original array element.

In Ruby, the block variable x is a copy of the element's value. Assigning x = x * 10 changes only x, not the original array element. So arr stays [1, 2, 3].

📝 Syntax

advanced

Identify the syntax error in this each block

Which option shows the correct way to write this each block without syntax errors?

Ruby

arr = [1, 2, 3]
arr.each do |x|
  puts x

A

arr.each |x| do
  puts x
end

B

arr.each do |x|
  puts x
end

C

arr.each do |x|
  puts x

D

arr.each do x |
  puts x
end

💡 Hint

Remember the syntax for blocks with do...end and pipes for block variables.

Option B correctly uses do |x| ... end. Option B has wrong order of pipes and do. Option B misses end. Option B has misplaced pipe.

🚀 Application

expert

Count how many elements are even using each

Using each as the primary iterator, what is the value of count after running this code?

Ruby

arr = [4, 7, 10, 3, 6]
count = 0
arr.each do |num|
  count += 1 if num.even?
end
puts count

A 4

B 2

C 3

D 5

💡 Hint

Check which numbers in the array are even and count them.

The even numbers are 4, 10, and 6. So count increases 3 times. The final count is 3.