# Write ac function to detect loop in a linkedin list

If you want a more formal proof that this works, you can examine the following resources: a question on our sister site; the Wikipedia cycle detection page; or "The Tortoise and the Hare Algorithm" by Peter Gammie, April 17, For example, node with value 5 in the above diagram.

If you're simply after support for the method not formal proofyou can run the following Python 3 program which evaluates its workability for a large number of sizes how many elements in the cycle and lead-ins elements before the cycle start.

If there is no end i. Since they will remain exactly size elements apart from each other at all times, tortoise will reach the start of the loop at exactly the same time as hare returns to the start of the loop.

### Length of loop in linked list

If you're simply after support for the method not formal proof , you can run the following Python 3 program which evaluates its workability for a large number of sizes how many elements in the cycle and lead-ins elements before the cycle start. After that start from the head of the Linked List and check for nodes one by one if they are reachable from ptr2. Let's return to the original position after you've found an element somewhere in the loop but you're not sure where the start of the loop is. We can also use Floyd Cycle Detection algorithm to detect and remove the loop. Write a C function to detect loop in a linked list Before trying to remove the loop, we must detect it. We can use this loop node to remove cycle. Otherwise, start the first pointer tortoise on the first node head, and the second pointer hare on the second node head. Then, as long as hare and tortoise are different, continue to advance hare, increasing size each time. Whenever we find a node that is reachable, we know that this node is the starting node of the loop in Linked List and we can get the pointer to the previous of this node.

First off, check if the list is empty head is null. Otherwise, set both hare and tortoise to the first element of the list and advance hare exactly size times to the 7 in this case.

Once you know a node within the loop, there's also an O n guaranteed method to find the start of the loop. Then loop continuously until hare is null which may be already true in a one-element listadvancing tortoise by one and hare by two in each iteration.

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