Hacker News Reader

Hmm, I was thinking 'in-place' in the context of 'no extra memory needed'. Is this not correct?

For sure, if it doesn't make sense to use a linked list in the first place then linked list merge sort definitely doesn't make sense...

View on HN

It's not that it's incorrect, it's that it's pointless. The entire point of a linked list is that you don't move around the data, you just re-link nodes. So any sane algorithm that works on linked lists is already "in-place" by default; an out-of-place merge on a linked list would be pure madness. So saying that an in-place merge can be performed on a data structure that already has some overhead and which already performs everything in place is not a very insightful or useful observation.

> an out-of-place merge on a linked list would be pure madness

Absolutely. I'm not even sure how you would do such a thing.

I personally have found it interesting when considering the difference between an array of pointers and a linked list, simply because they both have the same overhead but one doesn't require allocating any more memory for a merge sort.

I basically agree with what you say (maybe bar it not being useful knowledge) but I don't think it's worth continuing trying to clarify my initial statement.

Reply on news.ycombinator.com