Find length of Loop0

GeeksforGeeks

?? Problem Overview: Given the head of a linked list, the task is to determine whether the list contains a loop. If a loop is present, we need to return the number of nodes within the loop; otherwise, return 0.

??? Approach: To solve this problem, we can use Floyd’s Cycle-Finding Algorithm, also known as the Tortoise and Hare algorithm. This method helps in detecting loops efficiently and finding their length. Here's the step-by-step breakdown:

1. Initialization: Start by setting two pointers, slow and fast, both pointing to the head of the linked list.
2. Detecting the Loop: Move slow by one node and fast by two nodes.
3. If there's a loop, slow and fast will eventually meet. If fast reaches the end (null), then there's no loop.
4. Finding the Loop Length: Once a loop is detected (i.e., slow equals fast), keep one pointer fixed and move the other pointer one step at a time.
5. Count the number of steps until they meet again. This count gives the length of the loop.
6. Edge Cases: Consider edge cases where the list might be empty or have no loop (i.e., c = 0).

?? Code Implementation:

Here’s how the solution looks in Java:

?? Key Takeaways:

• Time Complexity: O(n) — Linear time for both detecting the loop and counting the nodes.
• Space Complexity: O(1) — Only a few pointers are used.

?? Conclusion:

Detecting loops in linked lists is a crucial operation in various applications, such as memory management and network topology analysis. By mastering this technique, you're equipped to handle more advanced problems involving linked data structures.