Longest Consecutive Sequence | DSA for Beginners | Hinglish Explanation

Описание: Welcome back to NullPointer Academy! 🚀
Yeh hai hamari DSA Playlist ka Ikkeesva (Day 21) video.
Aaj hum solve karenge ek super important interview problem — Longest Consecutive Sequence 🔥
Ye problem coding interviews aur online assessment rounds mein kaafi frequently poochhi jaati hai.

🔹 Problem Covered:

Array diya hota hai, hume longest length nikalni hoti hai jisme numbers consecutive ho (order matter nahi karta).

👉 Consecutive ka matlab:
x, x+1, x+2, x+3 …
👉 Elements array mein kisi bhi order mein ho sakte hain.

Example:
Input: [100, 4, 200, 1, 3, 2]
Output: 4
(Sequence: 1, 2, 3, 4)

🔹 Language:

Hinglish (Simple, clear aur beginner-friendly)

📌 What you’ll learn in this video:
✔ Brute Force Approach –

Har element ke liye check karna ki
kya x+1, x+2, x+3 … array mein present hain ya nahi.

❌ Repeated checks ki wajah se approach slow ho jaati hai
❌ Large input size ke liye inefficient

Time Complexity: O(N²)

✔ Better Approach (Sorting Based) –

✔ Pehle array ko sort karna
✔ Phir check karna ki next element exactly +1 hai ya nahi
✔ Duplicates ko properly handle karna

Is approach se unnecessary checks kam ho jaate hain.

Time Complexity: O(N log N)
Space Complexity: O(1)

✔ Optimal Approach (Interview Favourite) 🔥 –

✔ Unordered Set / Hash Set ka use
✔ Sirf wahi element sequence start karega jiska previous number exist nahi karta
✔ Ek single pass mein sequence ki length calculate karna

✨ No sorting
✨ No repeated traversal
✨ Clean logic

Time Complexity: O(N)
Space Complexity: O(N)

✔ Dry Run with Examples –

Step-by-step explanation ke saath arrays jaise:

[100, 4, 200, 1, 3, 2]
[0, 3, 7, 2, 5, 8, 4, 6, 0, 1]

Har approach ka visual dry run + clear intuition 🔍

✔ Pseudo Code Explanation –

✔ Language-independent pseudo code
✔ Logic pe focus — syntax pe nahi
✔ Viewers apni preferred language (C++, Java, Python, etc.) mein easily implement kar sakte hain

✔ Time & Space Complexity Analysis –

Teenon approaches ka clear comparison
Aur ye bhi discuss kiya gaya hai ki interview mein kaunsa approach best hai aur kyun

✔ Interview Insights –

✔ Common mistakes:

Har element se sequence start kar dena

Duplicates ignore na karna

Optimal approach ka intuition miss karna

✔ Edge cases:

Empty array

Single element

Duplicate values

Already consecutive elements

👉 Subscribe for Daily Hinglish DSA Videos:
   / @nullpointeracademy  

💬 Agar video pasand aaye to LIKE 👍, SHARE aur SUBSCRIBE karein.
Koi doubt ho to comments mein poochho — main help karne ke liye hoon 🚀