Module 2, Technical Preparation: Palindromes
Module Overview
Module 2 focuses on solving palindrome-related problems, a common type of challenge in technical interviews and coding assessments. A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward (ignoring spaces, punctuation, and capitalization).
Through this module, you'll learn various techniques to identify, validate, and manipulate palindromes, strengthening your string manipulation skills and problem-solving abilities.
Learning Objectives
- Solve a problem based on if a string is determined to be a palindrome
Understanding Palindromes
What are Palindromes?
A palindrome is a sequence that reads the same backward as forward. This concept applies to:
- Words: "radar", "level", "madam"
- Phrases: "A man, a plan, a canal, Panama" (ignoring spaces, commas, and case)
- Numbers: 121, 1001, 12321
Why are Palindromes Important in Technical Interviews?
Palindrome problems are popular in technical interviews because they:
- Test your string manipulation skills
- Can be solved with various approaches (iteration, recursion)
- Often involve edge cases that test your attention to detail
- Can be extended to more complex variants that test algorithmic thinking
Approaches to Solving Palindrome Problems
Two-Pointer Technique
The most efficient approach for checking palindromes is using the two-pointer technique:
- Place one pointer at the beginning of the string
- Place another pointer at the end of the string
- Move the pointers toward each other, comparing characters
- If any characters don't match, it's not a palindrome
- If the pointers meet or cross without finding mismatches, it is a palindrome
Reverse and Compare
Another common approach is to reverse the string and compare:
- Create a reversed copy of the string
- Compare the original string with the reversed string
- If they're identical, it's a palindrome
While this approach is intuitive, it requires extra space for the reversed string.
Advanced Palindrome Challenges
More complex palindrome problems may involve:
- Finding palindromic substrings
- Creating palindromes by rearranging characters
- Determining the minimum insertions needed to make a string palindromic
- Checking if a linked list is palindromic
Core Competencies
Palindrome Part 1 - Understand
Palindrome Part 2 - Plan
Palindrome Part 3 - Execute
Palindrome Part 4 - Reflect
Guided Project
In the guided project, we'll explore 2D Lists and Time Complexity (Big-O). This will help you understand more complex data structures and analyze the efficiency of your palindrome solutions.
2D Lists and Time Complexity
Module Assignment
To reinforce your understanding of palindrome problems and prepare for technical assessments, complete the following activities:
LeetCode Practice
For this sprint, we'll be using LeetCode to practice our problem-solving skills.
Assignment Tasks
- Log in to your LeetCode account
- Attempt at least 10 problems on your own, applying the 4-step problem-solving framework
- Complete at least 3 problems from the recommended list below
- Focus on problems involving string manipulation and palindromes
- For each problem:
- Apply the four-step problem-solving framework
- Document your thought process for each step
- Implement your solution and test it with the provided test cases
- After solving, review the Discussion section to see different approaches
- Analyze the time and space complexity of your solution
- Pay special attention to the "Understand" phase, ensuring you identify all edge cases
- Reflect on which steps of the framework were most challenging for you
- Practice explaining your approach as if you were in a technical interview
Recommended LeetCode Problems
- Valid Palindrome
- Valid Palindrome II
- Palindromic Substrings
- Longest Palindromic Substring
- Palindrome Partitioning
Regular practice is essential for success on the GCA. Focusing on palindrome problems will help you build critical string manipulation skills needed for the assessment.
General Code Assessment (GCA)
As part of this module, you will take the official General Code Assessment (GCA) test on CodeSignal. This standardized assessment evaluates your coding skills and provides a score that reflects your programming proficiency.
About the GCA:
- The assessment consists of 4 programming tasks to complete in 70 minutes
- You should aim for a score of 295 or higher
- Your highest score is tracked in the BloomTech database
Taking the GCA:
Remember: Regular practice on LeetCode problems using the 4-step problem-solving framework will help you succeed on the GCA. Focus on understanding problems thoroughly before implementing solutions.