How do you determine if a string is a palindrome?

Certainly! Let’s break down the concept of determining if a string is a palindrome. We’ll go step by step, with an example and a code implementation.

What is a Palindrome?

A palindrome is a string that reads the same backward as forward. For example:

• “madam” is a palindrome because it reads the same from left to right and right to left.
• “hello” is not a palindrome because it reads differently backward (“olleh”).

How to Determine if a String is a Palindrome

To determine if a string is a palindrome, follow these steps:

1. Normalize the String: Convert the string to a standard format. This usually involves:

• Converting all characters to the same case (lowercase or uppercase).
• Removing any spaces or special characters if you want to ignore them.

1. Reverse the String: Create a reversed version of the normalized string.
2. Compare: Check if the normalized string is equal to its reversed version. If they are the same, then the string is a palindrome.

Example

Let’s use the string “A man a plan a canal Panama” and determine if it is a palindrome.

1. Normalize the String:

• Convert to lowercase: “a man a plan a canal panama”
• Remove spaces: “amanaplanacanalpanama”

1. Reverse the String:

• Reversed version: “amanaplanacanalpanama”

1. Compare:

• Original normalized string: “amanaplanacanalpanama”
• Reversed string: “amanaplanacanalpanama”
• They are the same, so it is a palindrome.

Python Code

Here’s how you can write a simple Python function to check if a string is a palindrome:

def is_palindrome(s):
    # Step 1: Normalize the string
    normalized_string = ''.join(c.lower() for c in s if c.isalnum())

    # Step 2: Reverse the string
    reversed_string = normalized_string[::-1]

    # Step 3: Compare
    return normalized_string == reversed_string

# Example usage
example_string = "A man a plan a canal Panama"
if is_palindrome(example_string):
    print(f'"{example_string}" is a palindrome.')
else:
    print(f'"{example_string}" is not a palindrome.')

Detailed Explanation of the Code

1. Normalize the String:

• ''.join(c.lower() for c in s if c.isalnum()): This line does three things:
  • c.lower() converts each character to lowercase.
  • c.isalnum() checks if the character is alphanumeric (ignoring spaces and punctuation).
  • ''.join() combines all characters into a single string.

1. Reverse the String:

• normalized_string[::-1] creates a reversed version of the normalized string. The [::-1] slicing notation is used to reverse the string.

1. Compare:

• normalized_string == reversed_string checks if the original and reversed strings are the same.

This approach ensures that even if the original string contains spaces, punctuation, or different cases, the comparison will only consider the alphanumeric characters and will not be case-sensitive.