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A truly optimal sorting for a given N is a nontrivial problem. By truly optimal I mean the actual absolute minimum in the number of comparisons, no O(...) approximation.

For five elements the lower bound from counting the permutations is ceil(log2(5!)) which says you cannot sort 5 elements in less than 7 comparisons.

An actual 7 comparison algorithm exists but it is not very easy to write it. For greater numbers it gets much much trickier - in general the log(#permutations) lower bound cannot be met.

Agreed. My use of the word "optimal" in the original comment was a bit careless.

Hope my comment did not got across as a disagreement. Just wanted to add some relevant detail.

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