I have no idea why someone wouldn't want to use a built-in function. You tell me.
You're the one who's saying people should try to use the slowest possible algorithm.
Personally, if a tool provides provides a useful built in function, I'd use it.
If the tool doesn't provide something I need, I write my own function (or take a different approach).
And you're still missing the fundamental point. I never said anyone's O(n.log n) solutions wouldn't "work".
I was simply pointing out that claims that the data had to be sorted (resulting in a best case solution O(of n.log n)) are wrong and claims that the best solution is O(n.log n) are wrong. (Though I had originally attempted to avoid being so blunt about it.)
The claims are wrong because the problem is solvable without sorting; and a solution can be found in O(n) by anyone interested in digging a little deeper.
Really, the logic semantics behind my statements are quite trivial. I have no idea how I can explain it any more clearly to you.
I'd prefer it if this discussion doesn't get derailed by tangential rhetoric.
I was merely pointing out something that might motivate some people to dig a little deeper into the functions their language provides and the algorithms that can determine what values go where without needing to fully sort a list.
This is after all a learning site.