DAY 8 Exploring the Power of Hashmaps

Hello Everyone!

I’m Somuya Khandelwal, back with updates from Day 3 of Week 2 in my competitive programming journey. Today, I explored Hashmaps, a highly versatile data structure that simplifies data storage and retrieval. Hashmaps are invaluable for a wide range of problems, making them a cornerstone of efficient problem-solving.

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What I Worked On Today

1. Group Anagrams (Medium Difficulty)

   • Task: Group words that are anagrams into separate lists.
   • Approach:
     • Used a hashmap where the keys were either sorted versions of the strings or frequency counts of their characters.
     • Grouped words with the same key into corresponding lists.
   • What I Learned:
     • Sorting or character frequency can effectively generate unique identifiers for grouping.
     • Hashmaps are efficient for organizing and retrieving grouped data.

2. Happy Number (Easy Difficulty)

   • Task: Determine if repeatedly replacing a number with the sum of the squares of its digits leads to 1.
   • Approach:
     • Used a hashmap to track numbers encountered during the process.
     • Detected cycles by checking if a number repeated in the hashmap.
   • What I Learned:
     • Hashmaps are a powerful tool for tracking states and detecting cycles in iterative processes.
     • Problems with repetitive computations often benefit from memoization or cycle detection techniques.

3. Contains Duplicate II (Medium Difficulty)

   • Task: Check if a number in the array appears more than once within a given range k.
   • Approach:
     • Implemented a sliding window approach with a hashmap to store indices of recently seen numbers.
     • Compared indices dynamically to check for duplicates within the specified range.
   • What I Learned:
     • Combining hashmaps with sliding window techniques allows for efficient solutions to range-based problems.
     • Managing indices effectively is crucial for ensuring the accuracy of results in large input arrays.

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What I Learned Today

1. Using Hashmaps for Grouping and Counting:

   • Tasks like Group Anagrams showed how hashmaps simplify organizing data for efficient lookups and grouping.

2. Cycle Detection with Hashmaps:

   • The Happy Number problem illustrated how hashmaps can track visited states, making them ideal for identifying cycles.

3. Sliding Window with Hashmaps:

   • The combination of sliding windows and hashmaps, as seen in Contains Duplicate II, is a powerful technique for handling range-specific queries.

4. Edge Case Awareness:

   • For problems like Contains Duplicate II, handling scenarios such as small arrays or edge values for k is critical to ensure robust solutions.

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Reflections and Challenges

The Group Anagrams problem was particularly engaging, as it required creative thinking to develop unique grouping keys. Debugging the Happy Number problem was challenging but rewarding, as it reinforced the importance of efficiently tracking states to detect cycles.

Overall, today’s exercises strengthened my understanding of how hashmaps streamline problem-solving, especially when grouping, tracking, or managing data dynamically.

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Looking Ahead

Tomorrow, I’ll shift my focus to Binary Tree Problems, including Path Sum, Sum Root to Leaf Numbers, and Binary Tree Maximum Path Sum. These tasks will test my knowledge of recursion and tree traversal techniques.

Thank you for following along on my journey! Stay tuned for more updates and insights as I continue exploring the fascinating world of competitive programming.

Best,

Somuya