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Groups > comp.lang.c > #168673

Re: Compute Unique Numbers in a Set

From antispam@math.uni.wroc.pl
Newsgroups comp.lang.c
Subject Re: Compute Unique Numbers in a Set
Date 2022-12-28 01:32 +0000
Organization Aioe.org NNTP Server
Message-ID <tog6cb$pq4$1@gioia.aioe.org> (permalink)
References <todbqe$16sg$1@gioia.aioe.org>

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Albert <invalid@gmail.com> wrote:
> Is this the best way to generate unique random numbers in a set of 6 
> numbers?

"unique random numbers in a set of 6 numbers" is strange formulation
of the problem.  In such a small set you get at most 6 numbers
without repeating.  If you want exactly 6, this is (random) permutation
of original numbers.  There is standard, resonably efficient
algoritm for generating random permutations of N elements.  Assuming
numbering starting from 1, as step 1, swap number at first position N
with number at random postion (if random position happens to be N this
is a no-op).  Then recursively do generate random permutation of positions
1 to N - 1.  This is easy to implement as a loop, but presentation
is simpler in recursive way.

If you need less numbers than N, then you can use firs k < N positions
of random permutation.  Different methods make sense only if size
of your set (that in N) is much larger than number of random numbers
that you need (that is k).  For N = 6 there is no reason to do
anything more complicated than generating random permutation.

-- 
                              Waldek Hebisch

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Thread

Compute Unique Numbers in a Set Albert <invalid@gmail.com> - 2022-12-26 23:45 +0000
  Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-12-26 16:52 -0800
    Re: Compute Unique Numbers in a Set tTh <tth@none.invalid> - 2022-12-27 02:44 +0100
      Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-12-27 13:35 -0800
  Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-26 20:47 -0500
    Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 15:57 +0000
      Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 11:16 -0500
        Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 16:59 +0000
          Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 12:24 -0500
            Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 17:53 +0000
              Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 13:50 -0500
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 20:08 +0000
                Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 15:31 -0500
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-28 02:57 +0000
                Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 23:02 -0500
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-29 02:06 +0000
                Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-28 23:42 -0500
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-29 12:26 +0000
  Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-27 07:34 -0800
  Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 16:18 +0000
    Re: Compute Unique Numbers in a Set Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2022-12-28 01:08 +0000
      Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-28 03:30 +0000
    Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-27 19:42 -0800
  Re: Compute Unique Numbers in a Set Manu Raju <MR@invalid.invalid> - 2022-12-27 18:11 +0000
  Re: Compute Unique Numbers in a Set antispam@math.uni.wroc.pl - 2022-12-28 01:32 +0000
    Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 21:13 -0500
      Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-27 19:48 -0800
        Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 23:06 -0500
      Re: Compute Unique Numbers in a Set antispam@math.uni.wroc.pl - 2022-12-29 19:47 +0000
  Re: Compute Unique Numbers in a Set jak <nospam@please.ty> - 2022-12-28 11:28 +0100
  Re: Compute Unique Numbers in a Set Rosario19 <Ros@invalid.invalid> - 2023-01-01 21:06 +0100
    Re: Compute Unique Numbers in a Set Rosario19 <Ros@invalid.invalid> - 2023-01-02 06:43 +0100
  Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-01 23:19 +0000
    Re: Compute Unique Numbers in a Set jak <nospam@please.ty> - 2023-01-02 07:28 +0100
      Re: Compute Unique Numbers in a Set jak <nospam@please.ty> - 2023-01-02 08:48 +0100
      Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-01 23:53 -0800
        Re: Compute Unique Numbers in a Set Öö Tiib <ootiib@hot.ee> - 2023-01-02 01:18 -0800
    Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-02 13:49 +0000
  Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-02 12:27 +0000
  Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2023-01-02 12:13 -0500
    Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-02 17:31 +0000
      Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2023-01-02 12:46 -0500
      Re: Compute Unique Numbers in a Set Siri Cruise <chine.bleu@yahoo.com> - 2023-01-02 18:54 -0800
      Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-02 20:52 -0800
      Re: Compute Unique Numbers in a Set David Brown <david.brown@hesbynett.no> - 2023-01-03 09:01 +0100
      Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-03 07:28 -0800
        Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-03 15:46 +0000
          Re: Compute Unique Numbers in a Set David Brown <david.brown@hesbynett.no> - 2023-01-03 18:19 +0100
  Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 03:48 +0100
    Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 04:18 +0100
    Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-08 03:48 +0000
      Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 05:12 +0100
        Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 06:01 +0100
          Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-08 14:48 +0000
            Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 18:22 +0100
              Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-08 17:46 +0000
                Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-09 04:58 +0100
                Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-09 11:26 +0000
                Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-09 15:57 +0100
            Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-08 17:34 +0000
              Re: Compute Unique Numbers in a Set Ike Naar <ike@sdf.org> - 2023-01-08 21:45 +0000
                Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-08 23:13 +0000
                Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-08 15:18 -0800
          Re: Compute Unique Numbers in a Set Paavo Helde <eesnimi@osa.pri.ee> - 2023-01-08 21:19 +0200
          Re: Compute Unique Numbers in a Set "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2023-01-09 12:03 +0100
            Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-09 17:42 +0100
              Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-09 14:48 -0800
              Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-09 23:22 +0000
                Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-09 18:28 -0800
                Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-09 18:44 -0800
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-10 03:08 +0000
                Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-09 19:19 -0800
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-10 17:30 +0000
                Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-10 09:45 -0800
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-10 02:57 +0000
              Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-13 08:26 +0100
                Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-13 03:32 -0800
                Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-13 12:21 +0000
                Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-13 14:11 +0100
                Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-13 13:55 +0000
                Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-13 15:02 +0100
                Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-13 14:17 +0000
                Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-15 16:06 +0100
                Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-15 16:27 +0000
                Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-15 17:42 +0100
                Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-15 17:11 +0000
        Re: Compute Unique Numbers in a Set tTh <tth@none.invalid> - 2023-01-08 10:13 +0100
          Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 10:25 +0100
            Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-08 13:20 +0000
    Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-08 13:09 -0800
  Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-09 02:37 +0000
  Re: Compute Unique Numbers in a Set John Forkosh <forkosh@panix.com> - 2023-01-15 02:49 +0000

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