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date: 2025-07-23 topics: [dsa, algorithms, patterns, logic] day: 6

📘 Day 6 – More Core DSA Patterns & Problem Solving

✅ What I Worked On

• Solved & revised 7 more fundamental DSA problems
• Focused on how logic works under the hood, not just syntax
• Applied pattern recognition to reduce brute-force thinking

📚 What I Learned

Problem	Pattern / Concept
Sum of Digits	Use % 10 to extract digits, / 10 to reduce number
Factorial	Loop-based multiplication
Merge 2 Sorted Arrays	Two-pointer technique
Count Frequency	Use HashMap to map element → count
Missing Number	Use sum of n formula or XOR logic
Remove Duplicates	Use Set to eliminate repeats
Max Subarray Sum	Kadane’s Algorithm (dynamic programming)

Kadane’s Algorithm stood out — it feels magical how a greedy local sum helps track global max subarray!

❌ Blockers

• Remembering the XOR trick for missing number required extra practice
• Off-by-one mistakes in two-pointer merges

🧠 Reflection

DSA is starting to feel intuitive now. I’m seeing how many problems reuse similar ideas: pointers, hash maps, or math. Understanding the underlying patterns is 100x more effective than memorizing solutions.

🔗 References / Code

• 🧠 DSA Repo