Groups > comp.lang.java.programmer > #34318

Re: Mathematics, Java, good enough

From	Martin Gregorie <martin@address-in-sig.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: Mathematics, Java, good enough
Date	2016-05-17 12:24 +0000
Organization	A noiseless patient Spider
Message-ID	<nhf2ho$mg7$1@dont-email.me> (permalink)
References	<nhesp7$hn7$1@dont-email.me>

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On Tue, 17 May 2016 11:49:27 +0100, Duncan Idaho wrote:

> Hello again
> 
> I have a question that involves mathematics. I agree that it's off topic
> but as I am writing in Java I thought I'd give it a go (tenuous I know
> but it's the best I've got).
> 
> I'm dredging up set theory from the furthest reaches of my memory. I'll
> probably get it wrong.
> Homework? If only, that would mean I could have the last 50 years again
> ... perhaps not. %-)
> 
> Anyway
> 
> I have a set of characters S of cardinality C example if S = {a..z,
> 0..9, A..Z} then C = er, um  ..,62.
> 
> For any given result string X, X need not be a set.
> 
> eg if L = 8 then "abcdefgh", "AAAAAAAA", "AABBCCDD" are all valid values
> for X
> 
> how many strings of length L are possible from S
> 
> I don't even know what to call the question and I probably won't
> understand the answer but it will be fun trying.
>
Lets see - there are C ways to choose the first character and since, from 
your examples, the set members available for use as the second and 
subsequent positions aren't restricted by earlier choices, there are also 
C ways to choose the set member for all L positions in the result string.
This means there are C^N possible strings (C^N is C raised to the Nth 
power). 

Restating and calculating this in Java gives:

$ cat SetTheory.java 
public class SetTheory
{
   public static void main(String args[])
   {
      double possibleStrings = Math.pow(62, 8);
      System.out.println("62^8 = " + possibleStrings);
   }
}

$ javac SetTheory.java
$ java SetTheory
62^8 = 2.18340105584896E14
 

-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

Thread

Mathematics, Java, good enough Duncan Idaho <duncan@dunenoemail.com> - 2016-05-17 11:49 +0100
  Re: Mathematics, Java, good enough Eric Douglas <e.d.programmer@gmail.com> - 2016-05-17 04:55 -0700
  Re: Mathematics, Java, good enough Nigel Wade <nmw@ion.le.ac.uk> - 2016-05-17 12:56 +0100
    Re: Mathematics, Java, good enough Nigel Wade <nmw@ion.le.ac.uk> - 2016-05-17 13:06 +0100
    Re: Mathematics, Java, good enough Duncan Idaho <duncan@dunenoemail.com> - 2016-05-17 13:29 +0100
      Re: Mathematics, Java, good enough Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-17 09:54 -0400
        Re: Mathematics, Java, good enough FredK <fred.l.kleinschmidt@gmail.com> - 2016-05-17 07:17 -0700
          Re: Mathematics, Java, good enough FredK <fred.l.kleinschmidt@gmail.com> - 2016-05-17 07:29 -0700
            Re: Mathematics, Java, good enough Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-17 10:58 -0400
              Re: Mathematics, Java, good enough Duncan Idaho <duncan@dunenoemail.com> - 2016-05-17 18:10 +0100
                Re: Mathematics, Java, good enough Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-17 14:02 -0400
                Re: Mathematics, Java, good enough Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-17 14:10 -0400
                Re: Mathematics, Java, good enough Eric Douglas <e.d.programmer@gmail.com> - 2016-05-17 11:36 -0700
                Re: Mathematics, Java, good enough Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-17 16:12 -0400
                Re: Mathematics, Java, good enough Eric Douglas <e.d.programmer@gmail.com> - 2016-05-17 13:56 -0700
                Re: Mathematics, Java, good enough Gene Wirchenko <genew@telus.net> - 2016-05-17 14:13 -0700
                Re: Mathematics, Java, good enough Duncan Idaho <duncan@dunenoemail.com> - 2016-05-18 05:06 +0100
  Re: Mathematics, Java, good enough Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-17 08:25 -0400
  Re: Mathematics, Java, good enough Martin Gregorie <martin@address-in-sig.invalid> - 2016-05-17 12:24 +0000
  Re: Mathematics, Java, good enough Duncan Idaho <duncan@dunenoemail.com> - 2016-05-17 18:15 +0100
    Re: Mathematics, Java, good enough Jerry Stuckle <jstucklex@attglobal.net> - 2016-05-17 13:33 -0400
    Re: Mathematics, Java, good enough Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-17 14:09 -0400
      Re: Mathematics, Java, good enough Gene Wirchenko <genew@telus.net> - 2016-05-17 14:17 -0700
        Re: Mathematics, Java, good enough Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-17 17:49 -0400

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