Finding duplicates in a list

Question

I have a list of integer, and I want to know if the list contains any duplicates. My code is working, but I feel there is a more straightforward way of doing this

list1 = Range[10];
list2 = {1,2,3,4,1,6};
DoublesQ[list_] := Count[Tally[list], {_,n_}  /; n >1 ] == 0]

DoublesQ[list1]
=> True

DoublesQ[list2]
=> False

EDIT: So appears that Mathematica 10 has a function for that. I guess that now my question is: how can I do that without the build-in function?

@mete I think this one is a dup. There was a question with some performance figures for different methods, but I can't find it now. Someone will ... — Dr. belisarius, Nov 05 '14 at 17:36
I read this, but it seemed different from what I wanted: http://mathematica.stackexchange.com/questions/19357/counting-the-population-of-integers/19386#19386 — mete, Nov 05 '14 at 17:45

score 4 · Accepted Answer · answered Nov 05 '14 at 17:15

4

New in Mathematica 10 is the function DuplicateFreeQ

list1 = Range[10];
list2 = {1,2,3,4,1,6};

DuplicateFreeQ /@ {list1, list2}
(* {True, False} *)

answered Nov 05 '14 at 17:15

chuy

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Finding duplicates in a list

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