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Re^3: rand + shift || pop

by lidden (Deacon)
on Dec 21, 2010 at 15:58 UTC ( #878294=note: print w/ replies, xml ) Need Help??


in reply to Re^2: rand + shift || pop
in thread rand + shift || pop

Shuffleing is O(n) and spliceing is O(1), this may matter if your array is large.

Update: Oops, my understanding of splice was wrong. See JavaFan and ikegami below.


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Re^4: rand + shift || pop
by JavaFan (Canon) on Dec 21, 2010 at 16:41 UTC
    Actually, the expected running time of splicing is Ω(n), as a random splice will have to move n/4 elements on average.

    If you want to repeatedly get a random element (without duplication), shuffle the array and use pop or shift, for a linear running time. Repeatedly splicing a random element has an expected running time of Ω(n2).

Re^4: rand + shift || pop
by ikegami (Pope) on Dec 21, 2010 at 17:21 UTC
    It's only O(1) if you remove from the start or the end.

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