Use this tag on questions about algorithms that modify the data in-place, as opposed to making a copy
Merge sort is an O(n log n) worst-case comparison-based stable sorting algorithm.
Time space standard
"Another reason is that mergesort needs more memory because it s hard to implement it as an in-place sort"
from question "Quicksort slower than Mergesort?"
|Less space standard||
"1 in-place merge sort is used when you want to sort a list in o nlogn time while using less space than standard mergesort"
from question "In-place merge sort practical usage"
"Mergesort is more difficult to implement in-place but the out-of-place version is very cache-friendly - i suspect real-world implementations accept the o n space overhead - ram is cheap but memory bandwidth is a major bottleneck so trading memory for cache-efficiency and speed is often a good deal"
from question "Sorting in place"