Merge K Sorted Linked Lists - Leetcode 23 - Heaps (Python)

[@GregHogg]

Master Data Structures & Algorithms For FREE at AlgoMap.io!

[@chisomedoka5651]

The “Haha” moment that came after you mentioned heap. Your explanations are so clear, I love how you breakdown the problem and solution just before coding it out, I just might stand a chance with interviewing.

[@GregHogg]

Haha yeah, this is one of my favorite questions because of that!!

[@thetruth65756]

huge fan of neetcode but i gotta admit your solution for this problem is much easier to understand lol

[@mkhile1589]

Very good explanation.Your shorts video explanations are also so clear.

[@GregHogg]

Thank you glad to hear it!

[@Anantlahamge07]

Hey Greg, you said we need to add the values to the heap but in the code you added tuples in the heap. Why is that so? That's the only part I am confused about.

[@rajarshibiswas9424]

bro your explanation are really solid 👌 carry one

[@GregHogg]

Thank you!!

[@shantipriya370]

what an amazing explanation..

[@SeanKearney-g7d]

Is the merge sort type solution preferred over the heap solution?

[@knighthawk095]

How is this approach different from, flattening the input into a single list, sorting the list and then creating the linked list? *Food for thought*

[@igml1145]

It is more efficient to do the heap solution. Flattening the input will “lose” the information that the inner linked lists are sorted depending on the sorting algorithm that you use, as it might start making comparisons between elements of the same inner linked list

[@gabrielfonseca1642]

The total number of elements is n, so sorting the flattened list is O(nlogn) which is worse than O(nlogk).

[@tinutom810]

1st

[@christianjt7018]

I think the code is simpler if we just put all the nodes in the heap and then we start popping all the nodes from the heap. nodes = [] for l in lists: while l: heapq.heappush(nodes,(l.val,l)) l=l.next

[@GregHogg]

Simpler maybe, but slower! Then heap pops take log n time instead of log k time

[@christianjt7018]

@@GregHogg oh I see, thanks for the feedback