quartz/content/notes/07-mergesort-1.md

title	sr-due	sr-interval	sr-ease	tags
07-mergesort-1	2022-04-26	23	250	cosc201 lecture

mergeosrt

#unfinished

1 Divide and conquer

1. pre ⇒ break apartinto two or more smaller problems whose size add up to at most n
2. Rec ⇒ solve those problems recursively
3. post ⇒ combine solutions into a solution of the original problem

1.1 quicksort

pre ⇒ select pivot and split the array

rec ⇒ apply quicksort to the partitions

post ⇒ not much

designeds when sorting inplace was important

works best of primitive types as they can be stored in the fastest memory location

• memory access can be localised and the comparisions are direct
• those advantages are limited when sorting objects of reference type
• i that case each element of the array is just a reference to where the object really is
• so there are no local access advantages