Self-describing numbers

From Rosetta Code
Revision as of 13:31, 8 May 2011 by rosettacode>Paddy3118 (Modified to add clear task goals. - previous input may need adjusting.)
Self-describing numbers is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

There are several integers numbers called "self-describing".

Integers with the property that, when digit positions are labeled 0 to N-1, the digit in each position is equal to the number of times that that digit appears in the number.

For example 2020 is a four digit self describing number.

Position "0" has value 2 and there is two 0 in the number. Position "1" has value 0 because there are not 1's in the number. Position "2" has value 2 and there is two 2. And the position "3" has value 0 and there are zero 3's.

Self-describing numbers < 100.000.000: 1210 - 2020 - 21200 - 3211000 - 42101000

Task Description
  1. Write a function/routine/method/... that will check whether a given positive integer is self-describing.
  2. As an optional stretch goal - generate and display a few self-describing numbers.


BASIC

<lang qbasic>Dim x, r, b, c, n, m As Integer Dim a, d As String Dim v(10), w(10) As Integer Cls For x = 1 To 5000000

  a$ = ltrim$(Str$(x))
  b = Len(a$)
  For c = 1 To b
     d$ = Mid$(a$, c, 1)
     v(Val(d$)) = v(Val(d$)) + 1
     w(c - 1) = Val(d$)
  Next c
  r = 0
  For n = 0 To 10
     If v(n) = w(n) Then r = r + 1 
     v(n) = 0 
     w(n) = 0
  Next n
  If r = 11 Then Print x; " Yes,is autodescriptive number"

Next x Print Print "End" sleep end</lang>

J

<lang j> digits=: 10 #.inv ]

  digits 2020

2 0 2 0

  (,~ i.@#@digits)2020

0 1 2 3 2020

  (digits ,~ i.@#@digits)2020

0 1 2 3 2 0 2 0

  (,~ i.@#)&digits 2020

0 1 2 3 2 0 2 0

  _1 + #/.~@(,~ i.@#)&digits 2020

2 0 2 0

  (digits -: _1 + #/.~@(,~ i.@#)&digits) 2020

1

  (digits -: _1 + #/.~@(,~ i.@#)&digits) 1210

1

  (digits -: _1 + #/.~@(,~ i.@#)&digits) 21200

1

  (digits -: _1 + #/.~@(,~ i.@#)&digits) 3211000

1

  (digits -: _1 + #/.~@(,~ i.@#)&digits) 43101000

0

  (digits -: _1 + #/.~@(,~ i.@#)&digits) 42101000

1

  I. (digits -: _1 + #/.~@(,~ i.@#)&digits)"0 i.1e6

1210 2020 21200</lang>

<lang logo>TO XX BT MAKE "AA (ARRAY 10 0) MAKE "BB (ARRAY 10 0) FOR [Z 0 9][SETITEM :Z :AA "0 SETITEM :Z :BB "0 ]

  FOR [A 1 50000][
     MAKE "B COUNT :A
     MAKE "Y 0
     MAKE "X 0
     MAKE "R 0
     MAKE "J 0
     MAKE "K 0
  FOR [C 1 :B][MAKE "D ITEM :C :A
     SETITEM :C - 1 :AA :D 
     MAKE "X ITEM :D :BB 
     MAKE "Y :X + 1 
     SETITEM :D :BB :Y 
     MAKE "R 0]
  FOR [Z 0 9][MAKE "J ITEM :Z :AA 
     MAKE "K ITEM :Z :BB
     IF :J = :K [MAKE "R :R + 1]]

IF :R = 10 [PR :A] FOR [Z 0 9][SETITEM :Z :AA "0 SETITEM :Z :BB "0 ]] PR [END] END</lang>