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Google's “Director of Engineering” Hiring Test

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1764 points fatihky | 1 comments | 13 Oct 16 15:15 UTC | HN request time: 0.219s | source
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enjoylife ◴[13 Oct 16 15:48 UTC] No.12701550[source]▶
What the heck is a "Quicksort big-O score"? I've never heard anyone use the noun score when talking about complexity analysis.
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protomyth ◴[13 Oct 16 16:04 UTC] No.12701675[source]▶
I assume they want the average O(n log n), but who the heck knows given the script from above.

I get the feeling this: http://bigocheatsheet.com would come in handy

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steven777400 ◴[13 Oct 16 16:28 UTC] No.12701916[source]▶
Big-O technically means "worst case", which for Quicksort is O(n^2), although usually (in normal cases) it runs better than that. Other sort algorithms can guarantee not worse than O(n log n).
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1. susi22 ◴[13 Oct 16 17:16 UTC] No.12702370[source]▶
That's incorrect. The /mathematical/ definition means that it's the upper bound. I.e. yes, the set of all functions of O(N) is a subset of the set of all functions O(N^2). So you could say Quicksort is O(N^100) and still be technically correct.

However, the big-O notation does NOT specify anything about worst/avg/best-case complexity of a given algorithm. That should still be defined in the analysis.

You mixed up those two slightly different concepts.