Array modification (push, pop, shift, unshift) in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code?

Consider the following Ruby code snippet. What will be printed after all operations?

Ruby

arr = [1, 2, 3]
arr.push(4)
arr.shift
puts arr.inspect

A [4, 1, 2, 3]

B [1, 2, 3, 4]

C [2, 3, 4]

D [1, 2, 3]

💡 Hint

Remember that push adds to the end and shift removes from the start.

The array starts as [1, 2, 3]. push(4) adds 4 at the end, making it [1, 2, 3, 4]. Then shift removes the first element (1), leaving [2, 3, 4].

❓ Predict Output

intermediate

What does this Ruby code print?

Look at this code. What will be the output?

Ruby

arr = ['a', 'b', 'c']
arr.unshift('z')
arr.pop
puts arr.inspect

A ["z", "a", "b"]

B ["a", "b", "c", "z"]

C ["z", "a", "b", "c"]

D ["a", "b"]

💡 Hint

unshift adds at the start, pop removes from the end.

Starting with ['a', 'b', 'c'], unshift('z') adds 'z' at the front: ['z', 'a', 'b', 'c']. Then pop removes the last element 'c', resulting in ['z', 'a', 'b'].

❓ Predict Output

advanced

What is the final array after these operations?

Analyze the code and determine the final array content.

Ruby

arr = [10, 20, 30, 40]
arr.pop
arr.unshift(5)
arr.push(50)
arr.shift
puts arr.inspect

A [10, 20, 30, 50]

B [20, 30, 50]

C [5, 10, 20, 30]

D [5, 10, 20, 30, 50]

💡 Hint

Track each operation step-by-step.

Start: [10, 20, 30, 40]
pop removes 40 → [10, 20, 30]
unshift(5) adds 5 at front → [5, 10, 20, 30]
push(50) adds 50 at end → [5, 10, 20, 30, 50]
shift removes first element (5) → [10, 20, 30, 50]

❓ Predict Output

advanced

What error does this Ruby code raise?

Examine the code and identify the error it produces when run.

Ruby

arr = [1, 2, 3]
arr.pop(-5)
puts arr.inspect

A IndexError

B ArgumentError

C No error, outputs [1]

D TypeError

💡 Hint

Check the Ruby documentation for pop method arguments.

The pop method can take an optional argument for number of elements to remove. However, if the argument is negative, Ruby raises an ArgumentError.

🧠 Conceptual

expert

How many elements are in the array after these operations?

Given the code below, how many elements does the array contain at the end?

Ruby

arr = []
arr.unshift(1)
arr.push(2)
arr.unshift(3)
arr.pop
arr.shift
arr.push(4)
arr.shift

A 2

B 0

C 3

D 1

💡 Hint

Count carefully after each operation.

Start: []
unshift(1) → [1]
push(2) → [1, 2]
unshift(3) → [3, 1, 2]
pop removes last (2) → [3, 1]
shift removes first (3) → [1]
push(4) → [1, 4]
shift removes first (1) → [4]

Final array has 1 element.