Question

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Efficency of Insertion Sort vs Bubble sort vs Selection sort?

is selection sort faster than insertion for big arrays? When its in the worstest case?

I know insertion be faster than selection, but for large arrays and in the worstest case?

Answer 1

The size of the array involved is rarely of much consequence.

The real question is the speed of comparison vs. copying. The time a selection sort will win is when a comparison is a lot faster than copying. Just for example, let’s assume two fields: a single int as a key, and another megabyte of data attached to it.

In such a case, comparisons involve only that single int, so it’s really fast, but copying involves the entire megabyte, so it’s almost certainly quite a bit slower.

Since the selection sort does a lot of comparisons, but relatively few copies, this sort of situation will favor it. The insertion sort does a lot more copies, so in a situation like this, the slower copies will slow it down quite a bit.

As far as worst case for a insertion sort, it’ll be pretty much the opposite — anything where copying is fast, but comparison is slow. There are a few more cases that favor insertion as well, such as when elements might be slightly scrambled, but each is still within a short distance of its final location when sorted.

If the data doesn’t provide a solid indication in either direction, chances are pretty decent that insertion sort will work out better.