Comments for Umair's Blog

Comment on Finding the Start of a Loop in a Circular Linked List by Umair

Umair — Fri, 10 May 2013 13:27:35 +0000

During step-2, both pointers increment by *one*. So the path will be:

S: A-B-C
F: E-F-C

Thus, both of them meet at C.

Comment on Finding the Start of a Loop in a Circular Linked List by Naveen T

Naveen T — Thu, 09 May 2013 02:55:37 +0000

Simple and easy solution. Thanks

Comment on Finding the Start of a Loop in a Circular Linked List by Faisal Raza

Faisal Raza — Thu, 18 Apr 2013 08:05:38 +0000

You explained it excellently, a comprehensive solution.

Comment on Finding the Start of a Loop in a Circular Linked List by gururaj

gururaj — Sun, 10 Mar 2013 00:29:37 +0000

Hi Umair,
very nice explanation and helped me understand the solution clearly with the help of the images. However, you do not seem to have outlined the case when the loop length is smaller than the nodes traversed from the start to the loop head. I have tried to do it here: http://irrays.blogspot.in/2013/03/finding-loop-starter-of-linked-list.html
but have not been able to do it as clearly as you have.

Thanks for the post.

Comment on Finding the Start of a Loop in a Circular Linked List by Umair

Umair — Mon, 04 Mar 2013 13:18:38 +0000

Can you care to elaborate how this will be inefficient? Let’s start with the complexity. What do you think is the order of growth for this algorithm?

Comment on Finding the Start of a Loop in a Circular Linked List by Code Guru

Code Guru — Sat, 02 Mar 2013 05:15:42 +0000

Umair, this solution is efficient only for situation where length of loop is larger than distance from from the start to the loop point. Think of situation where loop is thousands of nodes away from start, but loop length is very small, say five nodes. Now you can see how inefficient this solution can be.

Comment on Finding the Start of a Loop in a Circular Linked List by ro

ro — Wed, 27 Feb 2013 09:16:19 +0000

Take a linked list A->B->C->D->E->F->C
Thus one can say C is start
1st step
S A – B – C – D – E – F
F A – C – E – C – E – C

so now they meet at E

2nd step
S A – B – C – D – E –
F E – C – E- C – E -

So here they meet again at E and not C. How you can find start of loop in this case? Correct me if I’m wrong

Comment on Snapshots in Xcode by Neerav Kothari

Neerav Kothari — Tue, 05 Feb 2013 03:15:31 +0000

is there a way to configure xcode for an automatic snapshot say like every time i hit run?

Comment on Snapshots in Xcode by kt

kt — Fri, 23 Nov 2012 09:10:17 +0000

Thank you.

Comment on Finding the Start of a Loop in a Circular Linked List by Umair

Umair — Fri, 09 Nov 2012 15:24:49 +0000

No. I think you did not quite get it, and your assertion that the algorithm works “only if the length of the cycle is more than the length of non-cyclic part” is incorrect.

In your example, the fast and the slow pointers will meet at node I, on the 8th increment for the slow pointer. The fact that there is a cycle in the list means that the fast pointer will have gone through the cycle twice before the fast & slow pointers meet. But they will meet. Step through and try it