PowerShell Script to Find Sum of Digits

Use $sum = ($number.ToString().ToCharArray() | ForEach-Object { [int]$_ }) | Measure-Object -Sum | Select-Object -ExpandProperty Sum to find the sum of digits of a number in PowerShell.

Examples

Input123

Output6

Input405

Output9

Input0

Output0

How to Think About It

To find the sum of digits, convert the number to a string so you can look at each digit separately. Then, change each character back to a number and add them all together.

Algorithm

1

Get the input number.

2

Convert the number to a string.

3

Split the string into individual characters.

4

Convert each character back to an integer.

5

Add all the integers together.

6

Return the sum.

Code

powershell

$number = Read-Host 'Enter a number'
$digits = $number.ToString().ToCharArray()
$sum = 0
foreach ($digit in $digits) {
    $sum += [int]$digit
}
Write-Output "Sum of digits: $sum"

Output

Enter a number: 123
Sum of digits: 6

Dry Run

Let's trace the input 123 through the code

1

Convert number to string and split

Input: 123 -> '123' -> ['1', '2', '3']

2

Convert each character to integer and sum

1 + 2 + 3 = 6

Digit	Integer Value	Running Sum
1	1	1
2	2	3
3	3	6

Why This Works

Step 1: Convert number to string

Using ToString() lets us treat the number as text to access each digit.

Step 2: Split into characters

Splitting into characters lets us handle each digit separately.

Step 3: Convert characters to integers and sum

Casting each character to [int] converts it back to a number so we can add them.

Alternative Approaches

Using Measure-Object

powershell

$number = Read-Host 'Enter a number'
$sum = ($number.ToString().ToCharArray() | ForEach-Object { [int]$_ }) | Measure-Object -Sum | Select-Object -ExpandProperty Sum
Write-Output "Sum of digits: $sum"

This method uses PowerShell's built-in Measure-Object to sum digits, making the code shorter and more readable.

Using array sum with pipeline

powershell

$number = Read-Host 'Enter a number'
$sum = 0
$number.ToString().ToCharArray() | ForEach-Object { $sum += [int]$_ }
Write-Output "Sum of digits: $sum"

This approach uses a pipeline with ForEach-Object to accumulate the sum, which is simple and clear.

Complexity: O(n) time, O(n) space

Time Complexity

The script processes each digit once, so time grows linearly with the number of digits.

Space Complexity

Converting the number to a character array uses extra space proportional to the number of digits.

Which Approach is Fastest?

Using Measure-Object is concise and efficient, but all methods have similar linear time complexity.

Approach	Time	Space	Best For
Loop with foreach	O(n)	O(n)	Clear step-by-step logic
Measure-Object	O(n)	O(n)	Concise and readable code
Pipeline with ForEach-Object	O(n)	O(n)	Simple and idiomatic PowerShell