PowerShell Script to Check Palindrome Number

Use a PowerShell script that converts the number to a string, reverses it with -join and Reverse, then compares it to the original string to check if it's a palindrome.

Examples

Input121

Output121 is a palindrome number.

Input123

Output123 is not a palindrome number.

Input1

Output1 is a palindrome number.

How to Think About It

To check if a number is a palindrome, think of it as a word. Convert the number to text, then reverse that text. If the reversed text matches the original, the number reads the same forwards and backwards, so it is a palindrome.

Algorithm

1

Get the input number as a string.

2

Reverse the string characters.

3

Compare the reversed string with the original string.

4

If they are the same, the number is a palindrome; otherwise, it is not.

Code

powershell

function Test-PalindromeNumber {
    param([int]$number)
    $str = $number.ToString()
    $rev = -join ($str.ToCharArray() | Reverse)
    if ($str -eq $rev) {
        Write-Output "$number is a palindrome number."
    } else {
        Write-Output "$number is not a palindrome number."
    }
}

Test-PalindromeNumber -number 121
Test-PalindromeNumber -number 123

Output

121 is a palindrome number.
123 is not a palindrome number.

Dry Run

Let's trace the number 121 through the code

1

Convert number to string

Input: 121 -> String: '121'

2

Reverse string characters

'121' reversed -> '121'

3

Compare original and reversed

'121' equals '121' -> True, so palindrome

Original String	Reversed String	Palindrome?
121	121	Yes

Why This Works

Step 1: Convert number to string

Using ToString() changes the number into text so we can check each character.

Step 2: Reverse the string

We split the string into characters, reverse their order with Reverse, then join them back with -join.

Step 3: Compare original and reversed

If the reversed string matches the original, the number reads the same forwards and backwards, so it is a palindrome.

Alternative Approaches

Using arithmetic to reverse number

powershell

function Test-PalindromeNumberArithmetic {
    param([int]$number)
    $original = $number
    $reverse = 0
    while ($number -gt 0) {
        $digit = $number % 10
        $reverse = $reverse * 10 + $digit
        $number = [math]::Floor($number / 10)
    }
    if ($original -eq $reverse) {
        Write-Output "$original is a palindrome number."
    } else {
        Write-Output "$original is not a palindrome number."
    }
}

Test-PalindromeNumberArithmetic -number 121
Test-PalindromeNumberArithmetic -number 123

This method uses math operations without converting to string, which can be faster for large numbers but is more complex to write.

Using string comparison with -eq operator

powershell

function Test-PalindromeNumberSimple {
    param([int]$number)
    $str = $number.ToString()
    if ($str -eq (-join ($str.ToCharArray() | Reverse))) {
        Write-Output "$number is a palindrome number."
    } else {
        Write-Output "$number is not a palindrome number."
    }
}

Test-PalindromeNumberSimple -number 121
Test-PalindromeNumberSimple -number 123

This is a concise version of the string reversal method, good for readability.

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

Time Complexity

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

Space Complexity

Extra space is used to store the reversed string, proportional to the number of digits.

Which Approach is Fastest?

The arithmetic method avoids string operations and can be faster for very large numbers, but the string method is simpler and clearer for most cases.

Approach	Time	Space	Best For
String reversal	O(n)	O(n)	Simplicity and readability
Arithmetic reversal	O(n)	O(1)	Performance with large numbers