What is your strategy for validating a string as a palindrome?

Question Analysis

The question is asking about a strategy to determine if a given string is a palindrome. A palindrome is a sequence of characters that reads the same forward and backward, ignoring spaces, punctuation, and capitalization. To effectively answer this question, you should outline a clear and efficient approach to check if a string meets these criteria. This involves understanding how to normalize the string (e.g., ignoring case and non-alphanumeric characters) and then checking its symmetry.

Answer

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

1. Normalize the String:

   • Convert the string to lowercase to ensure case insensitivity.
   • Remove all non-alphanumeric characters to focus only on the letters and numbers.

2. Check Symmetry:

   • Use two pointers to compare characters from the start and end of the normalized string.
   • Move the start pointer forward and the end pointer backward, checking for equality at each step.
   • If all corresponding characters are equal, the string is a palindrome; otherwise, it's not.

Here's a concise implementation in Python:

def is_palindrome(s: str) -> bool:
    # Normalize the string
    normalized = ''.join(char.lower() for char in s if char.isalnum())
    
    # Check symmetry using two pointers
    left, right = 0, len(normalized) - 1
    while left < right:
        if normalized[left] != normalized[right]:
            return False
        left += 1
        right -= 1
        
    return True

Key Points:

• Efficiency: This method is efficient with a time complexity of O(n), where n is the length of the string, due to the single pass check after normalization.
• Edge Cases: Consider empty strings and strings with only non-alphanumeric characters, which should be valid palindromes since they trivially satisfy the palindrome condition.