Write a function to determine if a given string is a permutation of a palindrome, where a palindrome reads the same forwards and backwards

Write a function to determine if a given string is a permutation of a palindrome, where a palindrome reads the same forwards and backwards

Write a function to determine if a given string is a permutation of a palindrome, where a palindrome reads the same forwards and backwards

Approach

To determine if a given string is a permutation of a palindrome, we need to follow a structured framework that includes:

  1. Normalize the String: Remove spaces and convert all characters to lowercase to ensure uniformity.

  2. Count Character Frequencies: Use a data structure to count the occurrences of each character.

  3. Evaluate Counts: For a string to be a permutation of a palindrome, at most one character can have an odd count.

Key Points

  • Definition of a Palindrome: A palindrome reads the same forwards and backwards (e.g., "racecar").

  • Character Frequency: In a palindrome, all characters must pair up with each other, leading to even counts, except for one character that can remain unpaired (for odd-length palindromes).

  • Efficiency: The algorithm should run in linear time (O(n)), where n is the length of the string.

Standard Response

Here is a Python function that implements the above approach:

def is_permutation_of_palindrome(s: str) -> bool:
 # Normalize the string
 normalized_str = ''.join(c.lower() for c in s if c.isalnum())
 
 # Count character frequencies
 char_count = {}
 for char in normalized_str:
 char_count[char] = char_count.get(char, 0) + 1
 
 # Check the counts for odd frequencies
 odd_count = 0
 for count in char_count.values():
 if count % 2 != 0:
 odd_count += 1
 
 # A valid palindrome permutation can have at most one odd character count
 return odd_count <= 1

# Example usage
print(is_permutation_of_palindrome("Tact Coa")) # Output: True
print(is_permutation_of_palindrome("Hello")) # Output: False

Tips & Variations

Common Mistakes to Avoid

  • Ignoring Non-Alphanumeric Characters: Remember to ignore spaces and punctuation when normalizing the string.

  • Case Sensitivity: Always convert characters to the same case to avoid mismatches.

  • Counting Logic: Ensure that you correctly count character frequencies; using a dictionary is often the easiest method.

Alternative Ways to Answer

  • Using Collections: Instead of a manual dictionary, use collections.Counter to simplify counting.

Role-Specific Variations

  • For Technical Roles: Focus on time and space complexity of the solution.

  • For Managerial Roles: Discuss the importance of clear logic and documentation for maintainability.

  • For Creative Roles: Emphasize the elegant solution and its adaptability for various input types.

Follow-Up Questions

  • Why is it important to normalize the string?

  • Can you explain how you would modify this function to handle unicode characters?

  • What edge cases did you consider while writing this function?

This structured approach not only provides a clear pathway to solving the problem but also aids job seekers in articulating their thought processes during technical interviews

Question Details

Difficulty
Medium
Medium
Type
Coding
Coding
Companies
Netflix
Amazon
Netflix
Amazon
Tags
Algorithm Development
Problem-Solving
Logical Thinking
Algorithm Development
Problem-Solving
Logical Thinking
Roles
Software Engineer
Data Scientist
Web Developer
Software Engineer
Data Scientist
Web Developer

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