Valid Palindrome

Step-by-Step Explanation

1. Initial Transformation : First, we'll convert all uppercase letters into lowercase letters because the case of the characters should not affect our palindrome check.
2. Filtering Alphanumeric Characters : We'll remove all non-alphanumeric characters (characters which are neither letters nor digits). Only alphanumeric characters will be used to form the new version of the string we need to check for being a palindrome.
3. Palindrome Check : We'll check if this newly formed string reads the same backward as it does forward.

Detailed Steps in Pseudocode:

4. Read the Input String : Start by reading the input string \( s \).
5. Initialize an Empty Result String : Create an empty string \( filtered\_string \) which will store the alphanumeric characters of the transformed input.
6. Iterate Over the Input String : Traverse each character in the input string \( s \).
• Convert Character to Lowercase : For each character, convert it to lowercase.
• Check if Character is Alphanumeric : Check if the character is alphanumeric (either a digit or a letter).
• Append if Alphanumeric : If the character is alphanumeric, append it to \( filtered\_string \).
7. Compare the Filtered String : Compare \( filtered\_string \) with its reverse to check if it forms a palindrome.
8. Return the Result : Return
   true
   if \( filtered\_string \) is the same forward and backward, otherwise return
   false
   .

Pseudocode with Comments

                                            
# Function to check if a string is a palindrome
FUNCTION isPalindrome(inputString):
# Step 1: Initialize an empty string to store the filtered characters
SET filtered_string TO EMPTY STRING

# Step 2: Traverse each character in the input string
FOR each character IN inputString:
# Convert the character to lowercase
SET lower_char TO LOWERCASE(character)

# Check if the character is alphanumeric
IF lower_char IS ALPHANUMERIC:
# Append the alphanumeric character to filtered_string
APPEND lower_char TO filtered_string

# Step 3: Compare the filtered string with its reverse
IF filtered_string IS EQUAL TO REVERSE(filtered_string):
# Step 4: Return true if it is a palindrome
RETURN true
ELSE:
# Step 4: Return false if it is not a palindrome
RETURN false

                                        

Explanation

9. Reading and Initializing : We start by reading the input string
   inputString
   and initializing an empty string called
   filtered_string
   to store our valid alphanumeric characters.
10. Iterate Over Input : We loop over each character in
    inputString
    . For each character, we convert it to lowercase to ensure uniformity.
11. Filter Alphanumeric Characters : Within the loop, we check if the lowercase character is alphanumeric. If it is, we append it to our
    filtered_string
    .
12. Palindrome Check : After building the filtered string with only lowercase alphanumeric characters, we compare it with its reverse version. If they match, the function returns
    true
    , indicating that the string is a palindrome. Otherwise, it returns
    false
    .