Day 89: Python Program to Check whether a String is Palindrome or not using Recursion

 

f is_palindrome_recursive(s):

    if len(s) <= 1:

        return True

     if s[0] != s[-1]:

        return False

    return is_palindrome_recursive(s[1:-1])

string = input("Enter a string: ")

processed_string = string.replace(" ", "").lower()

if is_palindrome_recursive(processed_string):

    print(f'"{string}" is a palindrome.')

else:

    print(f'"{string}" is not a palindrome.')

#source code --> clcoding.com 

Code Explanation:

def is_palindrome_recursive(s):

This line defines a function named is_palindrome_recursive, which will check whether a given string s is a palindrome.

A palindrome is a word, phrase, or sequence that reads the same forward and backward (ignoring spaces and capitalization).

    if len(s) <= 1:

        return True

This line checks if the length of the string s is less than or equal to 1.

If the string is empty or has only one character, it is trivially a palindrome, so the function returns True.

Example: "a", "b", or an empty string "" are all palindromes.

    if s[0] != s[-1]:

        return False

This checks if the first character (s[0]) is not equal to the last character (s[-1]).

If the first and last characters are not the same, the string cannot be a palindrome, so it returns False.

    return is_palindrome_recursive(s[1:-1])

If the first and last characters are the same, the function makes a recursive call with a substring that excludes the first and last characters (s[1:-1]).

This means the function will continue checking the inner characters of the string, ignoring the outer characters.

The recursion keeps narrowing the string until it either finds a mismatch (and returns False), or the string becomes too short to continue (and returns True).

Input Handling

string = input("Enter a string: ")

This line prompts the user to enter a string. The input is stored in the variable string.

processed_string = string.replace(" ", "").lower()

This line processes the string by removing any spaces with replace(" ", "") and converting all characters to lowercase using lower().

This ensures that the palindrome check is case-insensitive and doesn't consider spaces.

if is_palindrome_recursive(processed_string):

    print(f'"{string}" is a palindrome.')

else:

    print(f'"{string}" is not a palindrome.')

The if statement calls the is_palindrome_recursive function, passing the processed string (processed_string), which has no spaces and is in lowercase.

If the function returns True, it prints that the original string (string) is a palindrome.

If the function returns False, it prints that the original string is not a palindrome.