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MathGroup Archive 2005

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Re: Complement replacement

  • To: mathgroup at
  • Subject: [mg58632] Re: Complement replacement
  • From: Bill Rowe <readnewsciv at>
  • Date: Sun, 10 Jul 2005 16:51:59 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

On 7/10/05 at 5:12 AM, konstantpi at wrote:

>hi in the list: pp=Table[Random[Integer, {1, 1000}], {i, 1000}];
>how could i know which numbers from 1 to 1000 does not exist in the
>pp List. but without using: Complement[Table[i,{i,1000}],pp]

You could use


which is probably a bit more efficient. And if you wanted you could find ways to achieve the same result without using Complement. For example,


will group the set of numbers into blocks of contiguous integers. The missing integers could be found by looking at the last value of a block and the first value of the next block. But this is undoubtedly more computation than simply using Complement with Range as above.
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