I think a solution without extension function is better because the kata is for absolute beginners

Oh I think this one is my favourite!

This one is definitely the best.

God love whoever voted this a best practise :D

Nice! something to consider would be scanning the two arrays separately first to find the shortest and longest string, and then doing the comparison after.

Nice! A couple suggestions:

• The nested loops mean you're comparing every element against every other element, but notice that you really only have to compare the lengths of the longest and shortest string in each array, which you can find in a single pass on each array.
• You compute strlen on each element in each comparison, and strlen isn't cached in C, so you'll see a bunch of redundant length counts.