"All limits, especially national ones, are contrary to the nature of mathematics… Mathematics knows no races… For mathematics the whole cultural world is a single country" – David Hilbert. "Face problems with a minimum of blind calculation, a maximum of seeing thought" – Hermann Minkowski

Algorithms which are O(n), O(n log n), quadratic order, etc.

This video covers what you need to know for Decision Maths AS about “order” and “efficiency” of algorithms.

The terminology is a bit odd – the usual thing is to describe O(n), O(n^{2}), O(n log n) as the time-complexity of an algorithm and sometimes as its “efficiency”. Run-time usually means time, in actual seconds or whatever, on a particular computer in a particular implementation. But this video will do.