Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Computer Science Introduction to Data Structures Merge Sort and Linked Lists The Divide Step

Would we ever actually call split on a linked list with one node? I would think that would result in merge sort.

returning that item as naively sorted before it could be split. Thus you would never have a LinkedList with a value of None? Likewise, if the head was None then it would never be evaluated in the split function either since Merge_Sort would return it?

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,441 Points

Your observation is correct. As implemented, the main merge_sort code would quickly return if the linked_list contained one or fewer elements. Then why might the split function need to also content with a single node or empty list?

It is a good programming practice also to cover boundary conditions within the split function so it may be reused by other functions that need to split a linked list. This also lets the split function focus on its core job of always returning two object regardless of the input given.

A follow up question one might ask: if split handles the trivial list, why does merge_sort need to check for trivial cases? merge_sort needs to return on the trivial cases to end the recursive descent. Otherwise, split would continue to return the linked_list as left_half and none.

Post back if you need more help. Good luck!!!