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Detect start of a loop in linked list

Problem :

Given a linked list, implement an algorithm which returns the node at the beginning of the loop.

This post is a follow-up of
- JavaScript Linked List Example
- Detect a loop in cyclic/circular linked list.
- Loop Length in cyclic/cicular linked list.
I recommend reading those posts first, as the following code uses the methods from it.

Logic:

• Find the loop, using the same logic Detect a loop in cyclic/circular linked list.
• Move p1 at the head of the linked list, and keep p2 at the same location where p1 and p2 met.
• Move p1, p2 one step at a time, when they will meet again it's the beginning of the loop.

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This solution is a follow-up of JavaScript Linked List Example. I recommend reading it first, as the following code uses the method from it.

Solution :

Output :

References :

• Stackoverflow
• Floyd's algorithm for cycle detection

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