LeetCode Daily Challenge 🔥| DAY 90

🔥 LeetCode 219 – Contains Duplicate II | Java Solution | HashMap Explained

Can you detect duplicates within a given distance k? 📏

In this video, we solve LeetCode 219: Contains Duplicate II using an optimized HashMap approach.

💡 What You’ll Learn:

✅ Duplicate detection with index tracking
✅ HashMap optimization
✅ Distance validation logic
✅ Sliding window intuition
✅ Time & Space Complexity analysis

📌 Example

nums = [1,2,3,1]
k = 3

Duplicate:
1 at indices 0 and 3

Distance:
|3 - 0| = 3 ✔️

Output: true

🚀 Approach Used

1. Traverse array
2. Store value → last seen index
3. If duplicate found:
check distance greater or equals to k
4. Return true immediately

📈 Complexity

Time: O(n)
Space: O(n)

Perfect for coding interviews & DSA prep.

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