Array sorting and reversing in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sort the array in ascending order.

Ruby

numbers = [5, 3, 8, 1]
sorted_numbers = numbers.[1]

Drag options to blanks, or click blank then click option'

Ashuffle

Bsort

Creverse

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'reverse' instead of 'sort' will reverse the array but not sort it.

The sort method arranges the elements of the array in ascending order.

2fill in blank

medium

Complete the code to reverse the order of elements in the array.

Ruby

letters = ['a', 'b', 'c', 'd']
reversed_letters = letters.[1]

Drag options to blanks, or click blank then click option'

Areverse

Bpop

Csort

Dshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sort' will reorder elements alphabetically, not reverse them.

The reverse method flips the order of elements in the array.

3fill in blank

hard

Fix the error in the code to sort the array in descending order.

Ruby

scores = [10, 40, 30, 20]
desc_scores = scores.sort.[1]

Drag options to blanks, or click blank then click option'

Apop

Bsort

Cshuffle

Dreverse

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use 'sort' twice or using 'shuffle' which randomizes the array.

To sort in descending order, first sort ascending, then reverse the array.

4fill in blank

hard

Fill both blanks to create a new array with sorted elements and then reversed.

Ruby

data = [7, 2, 9, 4]
result = data.[1].[2]

Drag options to blanks, or click blank then click option'

Asort

Breverse

Cpop

Dshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'pop' or 'shift' which remove elements instead of sorting or reversing.

First, sort arranges the array ascending, then reverse flips it to descending.

5fill in blank

hard

Fill all three blanks to sort the array, reverse it, and then get the first element.

Ruby

values = [15, 3, 9, 7]
first = values.[1].[2].[3]

Drag options to blanks, or click blank then click option'

Asort

Breverse

Cfirst

Dlast

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'last' instead of 'first' will get the smallest element after reversing.

We sort ascending, reverse to descending, then get the first element which is the largest.

Practice

1. What does the Ruby method sort do when called on an array?

easy

A. It arranges the elements in ascending order.

B. It reverses the order of elements.

C. It removes duplicate elements.

D. It shuffles the elements randomly.

Solution

1. Step 1: Understand the purpose of sort

   The sort method arranges elements in ascending order by default.

2. Step 2: Compare with other methods

   Unlike reverse which flips order, sort orders elements from smallest to largest.

3. Final Answer:

   It arranges the elements in ascending order. -> Option A

4. Quick Check:

   sort = ascending order [OK]

Hint: Remember: sort arranges ascending, reverse flips order [OK]

Common Mistakes:

• Confusing sort with reverse
• Thinking sort removes duplicates
• Assuming sort shuffles elements

2. Which of the following is the correct syntax to reverse an array arr in Ruby?

easy

A. arr.reverse!

B. arr.reverse[]

C. reverse.arr()

D. arr.reverse()!

Solution

1. Step 1: Identify the correct method call

   The method to reverse an array in place is reverse! called on the array object.

2. Step 2: Check syntax correctness

   Only arr.reverse! is valid Ruby syntax; others are incorrect method calls or misplaced symbols.

3. Final Answer:

   arr.reverse! -> Option A

4. Quick Check:

   reverse! modifies array in place [OK]

Hint: Use reverse! to reverse array in place [OK]

Common Mistakes:

• Using parentheses incorrectly
• Placing exclamation mark after parentheses
• Calling reverse as a standalone function

3. What is the output of the following Ruby code?

arr = [3, 1, 4, 2]
sorted_arr = arr.sort
reversed_arr = sorted_arr.reverse
puts reversed_arr.inspect

medium

A. [1, 2, 3, 4]

B. [3, 1, 4, 2]

C. [4, 3, 2, 1]

D. [2, 4, 1, 3]

Solution

1. Step 1: Sort the original array

   Calling arr.sort returns a new array sorted ascending: [1, 2, 3, 4].

2. Step 2: Reverse the sorted array

   Calling sorted_arr.reverse flips the order to [4, 3, 2, 1].

3. Final Answer:

   [4, 3, 2, 1] -> Option C

4. Quick Check:

   sort then reverse = descending order [OK]

Hint: Sort then reverse = descending order [OK]

Common Mistakes:

• Assuming reverse modifies original array
• Confusing sorted array with original
• Expecting reverse to sort ascending

4. Identify the error in this Ruby code snippet:

arr = [5, 2, 9]
arr.sort!
arr.reverse
puts arr.inspect

medium

A. Missing parentheses in method calls cause errors.

B. The sort! method is invalid syntax.

C. The array arr cannot be reversed after sorting.

D. Using reverse does not change arr in place.

Solution

1. Step 1: Understand sort! effect

   sort! sorts the array arr in place, so arr becomes [2, 5, 9].

2. Step 2: Check reverse method usage

   reverse returns a new reversed array but does not modify arr itself.

3. Final Answer:

   Using reverse does not change arr in place. -> Option D

4. Quick Check:

   reverse without ! returns new array [OK]

Hint: Use reverse! to modify array in place [OK]

Common Mistakes:

• Assuming reverse changes original array
• Thinking sort! is invalid
• Believing method calls need parentheses always

5. Given an array arr = [7, 3, 5, 3, 9, 1], how can you create a new array that is sorted in descending order without changing the original array?

hard

A. Use arr.sort! then arr.reverse!

B. Use arr.sort.reverse

C. Use arr.reverse.sort

D. Use arr.reverse! then arr.sort!

Solution

1. Step 1: Sort the array without modifying original

   arr.sort returns a new sorted array ascending, original arr stays unchanged.

2. Step 2: Reverse the sorted array to get descending order

   Calling reverse on the sorted array returns a new array reversed, still not changing original.

3. Final Answer:

   Use arr.sort.reverse -> Option B

4. Quick Check:

   sort then reverse = descending new array [OK]

Hint: Chain sort then reverse to get descending without changing original [OK]

Common Mistakes:

• Using sort! or reverse! which modify original array
• Reversing before sorting
• Expecting reverse.sort to work the same