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Re: All componens different

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112008] Re: All componens different
  • From: Alexei Boulbitch <alexei.boulbitch at iee.lu>
  • Date: Tue, 24 Aug 2010 06:14:23 -0400 (EDT)

Hello, Wolfgang,
one idea would be to use the property of the function Union[] to sort with deleting duplicates
and to draw the conclusion on the basis of the length comparison:

allDifferent1[v_List] := SameQ[Length[Union[v]], Length[v]];

or like this (which is all the same):

allDifferent2[v_List] := Length[#] & /@ SameQ[Union[v], v];

(* Below there are two lists to test it *)
(* u has all different terms, v has some terms equal to one another *)

u = Range[25];
v = Table[RandomInteger[{0, 5}], {25}]

allDifferent1[u]
allDifferent1[v]

True

False

Regards, Alexei


Given a list v of natural numbers I'm looking for a function d[v_] that 
returns True if all components are different and False otherwise.

One solution is

d1[v_] := ! Or @@ Flatten[Table[v[[i]] == v[[k]], {i, 1, Length[v]}, 
{k, i + 1, Length[v]}]]

Can you find more efficient (and elegant) solutions?

Regards,
Wolfgang 


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