Arrays in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this PowerShell array operation?

Consider the following PowerShell code snippet. What will be the output after running it?

PowerShell

$arr = 1,2,3,4,5
$arr[1..3]

A 2 3 4

B 3 4 5

C 1 2 3

D 1 3 5

💡 Hint

Remember that array slicing with [start..end] includes both start and end indices.

The slice $arr[1..3] selects elements at indices 1, 2, and 3, which are 2, 3, and 4 respectively.

📝 Syntax

intermediate

Which option correctly creates an array of strings in PowerShell?

Select the option that correctly creates an array containing the strings "apple", "banana", and "cherry".

A $fruits = {'apple', 'banana', 'cherry'}

B $fruits = ['apple', 'banana', 'cherry']

C $fruits = @('apple', 'banana', 'cherry')

D $fruits = array('apple', 'banana', 'cherry')

💡 Hint

PowerShell uses @() to create arrays.

Option C uses the correct syntax @() to create an array. Options B, C, and D are invalid in PowerShell for array creation.

🔧 Debug

advanced

Why does this PowerShell array code produce an error?

The following code is intended to add an element to an existing array, but it causes an error. What is the reason?

PowerShell

$arr = 1,2,3
$arr += 4
$arr[3]

A Error because arrays in PowerShell are fixed size and cannot be appended

B No error occurs; output is 4

C Error because += operator is not valid for arrays

D Error because $arr[3] is out of range

💡 Hint

Try running the code in PowerShell to see the actual behavior.

In PowerShell, += on arrays creates a new array with the added element. So $arr becomes 1,2,3,4 and $arr[3] is 4.

🚀 Application

advanced

How to filter an array to only even numbers in PowerShell?

Given an array $numbers = 1..10, which option correctly filters it to only even numbers?

PowerShell

$numbers = 1..10

A $even = $numbers | Where-Object { $_ % 2 -eq 0 }

B $even = $numbers.Where({ $_ % 2 -eq 0 })

C $even = $numbers | Filter { $_ % 2 -eq 0 }

D $even = $numbers | Select-Object { $_ % 2 -eq 0 }

💡 Hint

Use the correct cmdlet for filtering in PowerShell pipelines.

Where-Object is the correct cmdlet to filter elements in a pipeline. Options A, B, and D are invalid or incorrect usage.

🧠 Conceptual

expert

What is the length of the array after this PowerShell operation?

Given the code below, what is the length of $arr after execution?

PowerShell

$arr = 1,2,3
$arr = $arr + @(4,5)
$arr = $arr[1..3]

A 2

B 5

C 4

D 3

💡 Hint

Track the array length after each operation carefully.

Initially $arr has 3 elements. After adding @(4,5), it has 5 elements. Then slicing [1..3] selects 3 elements, so length is 3.

Practice

1. What does an array in PowerShell do?

easy

A. Stores only one item at a time

B. Stores multiple items in one variable

C. Runs commands sequentially

D. Creates a new script file

Solution

1. Step 1: Understand the purpose of arrays

   Arrays hold multiple values together in one variable, unlike single variables that hold one value.

2. Step 2: Compare options with array definition

   Only Stores multiple items in one variable correctly describes storing multiple items in one variable, which matches the array concept.

3. Final Answer:

   Stores multiple items in one variable -> Option B

4. Quick Check:

   Arrays = store multiple items [OK]

Hint: Arrays hold many items together in one variable [OK]

Common Mistakes:

• Thinking arrays hold only one item
• Confusing arrays with scripts or commands
• Believing arrays create files

2. Which of the following is the correct way to create an empty array in PowerShell?

easy

A. $arr = []

B. $arr = array()

C. $arr = {}

D. $arr = @()

Solution

1. Step 1: Recall PowerShell array syntax

   PowerShell uses @() to create arrays, including empty ones.

2. Step 2: Check each option

   $arr = @() uses @() which is correct. Options A, B, and C use invalid or different syntax for arrays.

3. Final Answer:

   $arr = @() -> Option D

4. Quick Check:

   Empty array = @() [OK]

Hint: Use @() to create arrays in PowerShell [OK]

Common Mistakes:

• Using [] which is not valid for arrays in PowerShell
• Using {} which is for hashtables or script blocks
• Using array() which is not recognized in PowerShell

3. What is the output of this PowerShell code?

$arr = @('apple', 'banana', 'cherry')
Write-Output $arr[1]

medium

A. banana

B. apple

C. cherry

D. 1

Solution

1. Step 1: Understand array indexing in PowerShell

   Arrays start at index 0, so $arr[0] = 'apple', $arr[1] = 'banana', $arr[2] = 'cherry'.

2. Step 2: Identify the output of $arr[1]

   The code outputs the item at index 1, which is 'banana'.

3. Final Answer:

   banana -> Option A

4. Quick Check:

   Index 1 = banana [OK]

Hint: Arrays start at zero; index 1 is second item [OK]

Common Mistakes:

• Thinking index starts at 1
• Confusing item values with index numbers
• Expecting all items printed instead of one

4. Identify the error in this PowerShell code:

$arr = @()
$arr + 'orange'

medium

A. += operator is missing to add item

B. Array cannot be empty

C. Use [] instead of @() for arrays

D. Variable name must start with capital letter

Solution

1. Step 1: Check how to add items to arrays

   In PowerShell, to add an item to an array, use '+=' operator, not just '+'.

2. Step 2: Analyze the code

   The code uses '$arr + 'orange'' which does not update $arr. It should be '$arr += 'orange'' to add the item.

3. Final Answer:

   += operator is missing to add item -> Option A

4. Quick Check:

   Add item with += [OK]

Hint: Use += to add items to arrays, not just + [OK]

Common Mistakes:

• Using + without = to add items
• Thinking arrays cannot be empty
• Confusing array syntax with other languages

5. You have an array $arr = @('cat', 'dog', 'bird'). How do you add 'fish' to the end and then print all items one per line?

hard

A. $arr = $arr + 'fish'; Write-Host $arr

B. $arr + 'fish'; Write-Output $arr

C. $arr += 'fish'; $arr | ForEach-Object { Write-Output $_ }

D. $arr += 'fish'; Write-Host $arr[0], $arr[1], $arr[2], $arr[3]

Solution

1. Step 1: Add 'fish' to the array correctly

   Use '+=' operator to add 'fish' to $arr: $arr += 'fish'.

2. Step 2: Print each item on its own line

   Use pipeline with ForEach-Object and Write-Output to print each item separately.

3. Step 3: Check each option

   $arr += 'fish'; $arr | ForEach-Object { Write-Output $_ } correctly adds and prints items line by line. $arr + 'fish'; Write-Output $arr does not update $arr. $arr = $arr + 'fish'; Write-Host $arr uses Write-Host which prints all items on one line. $arr += 'fish'; Write-Host $arr[0], $arr[1], $arr[2], $arr[3] prints items but manually and is less flexible.

4. Final Answer:

   $arr += 'fish'; $arr | ForEach-Object { Write-Output $_ } -> Option C

5. Quick Check:

   Add with += and print with pipeline [OK]

Hint: Add with += and print each item using pipeline [OK]

Common Mistakes:

• Using + without = to add items
• Printing array without pipeline for separate lines
• Using Write-Host which prints all on one line