What should students be taught first when first learning sorting algorithms? [closed]

Answer 1

If you can ultimately only teach ONE algorithm at all, I think SelectionSort is even easier to teach (and implement IMHO) as BubbleSort. It might be ultra ineffectively, but everyone will get its concept, everyone with a little programming knowledge can read its code and there is one thing that makes SelectionSort rather unique among all sorting algorithms: It only needs n - 1 swaps for a list of n entries :-) Not only that it never needs to make more than n - 1 swaps, it actually needs exactly n - 1 swaps. The number of swaps performed is 100% deterministic and known before it even starts. I think this is not true for any other in-place sorting algorithm (though people are free to correct me in comments).

Otherwise I vote for BubbleSort and SelectionSort, those are easiest to understand and show how sorting the easy way (these are simple enough, students may actually come up with these solutions without ever having heard of any sorting algorithm) is sometimes not very effective. In contrast I'd show QuickSort and MergeSort, being very good divide and conqueror algorithms and both also very fast.

Algorithms I'd not use, as their concept is harder to get, are ShellSort, RadixSort, HeapSort, and BucketSort. Also they are rather special (you usually only use them when sorting certain kind of data or if you have certain constrains for sorting).

You might mention the little sister of ShellSort, InsertionSort (which is basically a shell sort where the step width has finally reach one), but only because many QuickSort implementation use InesrtionSort as fall-back sort, once the recursion gets too deep (or the remaining data set to sort recursively gets too small)... but here it starts getting really complicated and you shouldn't make it too complicated.

Answer 2

best lecture I ever attended on algorithms demonstrated all of them as bar-graphs drawn via java applets. You could then see the pattern of sorting as well as the O(N) characteristics as well...

Teach bubble because its incredibly simple and show the rest as animations maybe?

Answer 3

I think sorting methods are a very good example of what an algorithm is. But it only becomes a good example when you compare various methods. If you can only teach one, I'm not sure it's worthwhile.

Realisticly, we call the sort method in some framework. So if you can't effectively teach about the sorting alorithms, it might not be worth the time.

Nobody has to write a sort method anymore, but it's still a very good example of the impact of algorithms.

Answer 4

Keeping in mind that your student will probably never have to code a sort themselves, the question really should be decided on "what is the value of learning this algorithm?" instead of "what does this algorithm do?"

In other words, your students should be taught a variety of different algorithms -- whether they are for sorting, searching, compressing etc is largely irrelevant.

Answer 5

Bubble sort is the easiest one for beginners to grok, and it also serves as an excellent example of why easy solutions can be expensive. Could be a good way to segue into asymptotic complexity and big-O notation?

Answer 6

I would teach the "call the framework" sort.

It would be efficient to teach and learn this sort. Students would have a high degree of success and low error rate with implementing this sort.

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Edit: There are a lot of criticizing comments on this answer about the quality of my single sort class. These criticisms are applicable to any answer to this question, which is - "If you were a programming teacher and you had to choose one sorting algorithm to teach your students which one would it be?"