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Every element in List A appears only once, and the same is true for List B. How can I efficiently create a list of the element in A that don't appear in B? Obviously, I can just do this:

Do[A=DeleteDuplicates[A,B[[i]]],{i,1,Length[B]}];

...but that's painfully slow for very long lists. Also, it doesn't take advantage of my knowledge that every element in each list is unique within the list.

Thanks!

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    $\begingroup$ Complement[B, A] ? $\endgroup$ – cvgmt Mar 7 at 23:15
  • $\begingroup$ @cvgmt Seriously, that simple? Well, if you want to post that as an Answer, I'll Accept it. $\endgroup$ – Jerry Guern Mar 7 at 23:17
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A = RandomInteger[10, 10]
B = RandomInteger[10, 8]
Complement[A, B]
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