Array sorting and reversing 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 it print?

Ruby

arr = [5, 3, 8, 1]
puts arr.sort.reverse.join(",")

A "1,3,5,8"

B "8,5,3,1"

C "5,3,8,1"

D "8,3,5,1"

💡 Hint

Think about what sort and reverse do to the array.

The code sorts the array in ascending order: [1,3,5,8], then reverses it to descending order: [8,5,3,1], then joins elements with commas.

❓ Predict Output

intermediate

What does this Ruby code print?

Look at this Ruby code. What will be printed?

Ruby

arr = ["dog", "cat", "bird"]
puts arr.sort.reverse[0]

A "error"

B "bird"

C "dog"

D "cat"

💡 Hint

Sort alphabetically, then reverse, then pick first element.

Sorting alphabetically gives ["bird", "cat", "dog"]. Reversing gives ["dog", "cat", "bird"]. The first element is "dog".

🔧 Debug

advanced

Why doesn't this Ruby code sort and reverse the original array?

This Ruby code is intended to sort and reverse the original array in place, but the original array remains unchanged. What is the cause?

Ruby

arr = [1, 2, 3]
arr.sort.reverse!
puts arr

A sort returns a new array; reverse! modifies the new array but leaves the original unchanged

B No error; code runs and prints "3\n2\n1"

C reverse! is not a valid method in Ruby

D reverse! returns nil and causes puts to print nothing

💡 Hint

Check what sort and reverse! do to the array.

sort returns a new sorted array [1,2,3]. reverse! reverses that new array in place to [3,2,1]. The original arr remains [1,2,3], so puts arr prints 1 2 3 each on a new line. No runtime error.

🧠 Conceptual

advanced

How many elements are in the array after this Ruby code?

What is the number of elements in the array after running this code?

Ruby

arr = [4, 7, 2, 9]
new_arr = arr.sort.reverse.select { |x| x > 5 }

A 1

B 3

C 4

D 2

💡 Hint

Sort, reverse, then select elements greater than 5.

Sorted ascending: [2,4,7,9], reversed: [9,7,4,2], select >5: [9,7], so 2 elements.

❓ Predict Output

expert

What is the output of this Ruby code with mixed types?

What will this Ruby code print?

Ruby

arr = ["10", 2, "3", 1]
sorted = arr.sort_by { |x| x.to_i }.reverse
puts sorted.join("-")

A "10-3-2-1"

B "error"

C "10-2-3-1"

D "3-10-2-1"

💡 Hint

Convert all elements to integers for sorting, then reverse.

to_i converts strings to integers: [10,2,3,1]. Sorted ascending: [1,2,3,10]. Reversed: [10,3,2,1]. Joined with '-' gives "10-3-2-1".