How do you write a function to check if one string is a permutation of another string?

How do you write a function to check if one string is a permutation of another string?

How do you write a function to check if one string is a permutation of another string?

Approach

To effectively answer the question "How do you write a function to check if one string is a permutation of another string?", follow this structured framework:

  1. Understand the Problem: Define what a permutation is and how it relates to strings.

  2. Identify Requirements: Consider case sensitivity, whitespace, and character types.

  3. Choose an Approach: Decide between sorting, counting characters, or using data structures.

  4. Implement the Solution: Write clean, efficient code.

  5. Test Your Function: Validate with various test cases.

Key Points

  • Definition of Permutation: A string is a permutation of another if it contains the same characters in a different order.

  • Considerations:

  • Case Sensitivity: Determine if 'abc' and 'ABC' should be considered permutations.

  • Whitespace: Decide if spaces should be ignored in comparisons.

  • Character Set: Consider if you only want to check for alphanumeric characters.

  • Efficiency: Choose an approach that balances readability and performance, especially for large strings.

Standard Response

Here’s a sample implementation in Python to check if one string is a permutation of another:

def are_permutations(str1, str2):
 # Normalize the strings: remove spaces and convert to lowercase
 str1 = str1.replace(" ", "").lower()
 str2 = str2.replace(" ", "").lower()

 # If lengths are different, they cannot be permutations
 if len(str1) != len(str2):
 return False

 # Sort both strings and compare
 return sorted(str1) == sorted(str2)

# Example usage
str1 = "Listen"
str2 = "Silent"
print(are_permutations(str1, str2)) # Output: True

Explanation:

  • Normalization: We first remove spaces and convert both strings to lowercase for a fair comparison.

  • Length Check: If the strings have different lengths, we immediately return False.

  • Sorting: By sorting both strings, we can easily compare their characters. If they are identical after sorting, they are permutations.

Tips & Variations

Common Mistakes to Avoid

  • Ignoring Case Sensitivity: Not normalizing strings can lead to incorrect results.

  • Not Checking Length: Failing to check the length first can lead to unnecessary computation.

  • Using Inefficient Algorithms: Sorting has a time complexity of O(n log n); consider using a counting method for better performance.

Alternative Ways to Answer

  • Character Counting: Instead of sorting, you could count occurrences of each character using a dictionary or a list.

Role-Specific Variations

  • Technical Roles: Focus on performance and edge cases, emphasizing time complexity.

  • Managerial Roles: Discuss how you would approach the problem with a team, including code reviews and testing strategies.

  • Creative Roles: If the question arises in a creative context, emphasize problem-solving and thinking outside the box.

Follow-Up Questions

  • What edge cases did you consider?

  • Discuss handling empty strings, special characters, or very large inputs.

  • Can you optimize your solution further?

  • Explore using a one-pass algorithm with a hash map for character counting.

  • How would you implement this in a different programming language?

  • Discuss language-specific features and data structures that could be used.

This comprehensive guide provides a structured approach to answering the interview question on permutations, helping job seekers craft strong, SEO-optimized responses while preparing effectively for technical interviews

Question Details

Difficulty
Medium
Medium
Type
Coding
Coding
Companies
Intel
IBM
Intel
IBM
Tags
Programming
Problem-Solving
Logical Thinking
Programming
Problem-Solving
Logical Thinking
Roles
Software Engineer
Data Scientist
Technical Analyst
Software Engineer
Data Scientist
Technical Analyst

Ace Your Next Interview with Real-Time AI Support

Get real-time support and personalized guidance to ace live interviews with confidence.

Interview Copilot: Your AI-Powered Personalized Cheatsheet

Interview Copilot: Your AI-Powered Personalized Cheatsheet

Interview Copilot: Your AI-Powered Personalized Cheatsheet