Proper divisors: Difference between revisions
add REXX
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<pre>[set(), {1}, {1}, {1, 2}, {1}, {1, 2, 3}, {1}, {1, 2, 4}, {1, 3}, {1, 2, 5}]
15120 79</pre>
=={{header|REXX}}==
<lang rexx>Call time 'R'
Do x=1 To 10
Say x '->' proper_divisors(x)
End
hi=1
Do x=1 To 20000
/* If x//1000=0 Then Say x */
npd=count_proper_divisors(x)
Select
When npd>hi Then Do
list.npd=x
hi=npd
End
When npd=hi Then
list.hi=list.hi x
Otherwise
Nop
End
End
Say hi '->' list.hi
Say ' 166320 ->' count_proper_divisors(166320)
Say '1441440 ->' count_proper_divisors(1441440)
Say time('E') 'seconds elapsed'
Exit
proper_divisors: Procedure
Parse Arg n
If n=1 Then Return ''
pd=''
/* Optimization reduces 37 seconds to 28 seconds */
If n//2=1 Then /* odd number */
delta=2
Else /* even number */
delta=1
Do d=1 To n%2 By delta
If n//d=0 Then
pd=pd d
End
Return space(pd)
count_proper_divisors: Procedure
Parse Arg n
Return words(proper_divisors(n))</lang>
{{out}}
<pre>1 ->
2 -> 1
3 -> 1
4 -> 1 2
5 -> 1
6 -> 1 2 3
7 -> 1
8 -> 1 2 4
9 -> 1 3
10 -> 1 2 5
79 -> 15120 18480
166320 -> 159
1441440 -> 287
28.342000 seconds elapsed</pre>
=={{header|Ruby}}==
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