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Leetcode 287 – Find the Duplicate Number | Python | Fast & Slow Pointers (Floyd's Algorithm)

In this video, we solve the popular Find the Duplicate Number problem using an optimized approach — Floyd’s Tortoise and Hare Algorithm (a.k.a. Cycle Detection).

The input array is treated like a linked list, where each index points to the next number. A duplicate number causes a cycle, and we detect it without modifying the array or using extra space.

Key Concepts Covered:
How to model the array as a linked list with a cycle

Why the duplicate creates a cycle

Applying Floyd’s Tortoise and Hare Algorithm

Finding the entry point of the cycle (duplicate)

Step-by-step Python code explanation

Time and space analysis

Why this approach is better than brute force or sorting

🧪 Time & Space Complexity:
Time: O(n)

Space: O(1) (No extra space needed)

🔗 Problem Link:
Leetcode 287 – Find the Duplicate Number

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