Amicable pairs: Difference between revisions

---Functional===

----

===Straightforward===

… and about 55 times as fast as the above.

<syntaxhighlight lang="applescript">on properDivisors(n)

set output to {}

if (n > 1) then

set sqrt to n ^ 0.5

set limit to sqrt div 1

if (limit = sqrt) then

set end of output to limit

set limit to limit - 1

end if

repeat with i from limit to 2 by -1

if (n mod i is 0) then

set beginning of output to i

set end of output to n div i

end if

end repeat

set beginning of output to 1

end if

return output

end properDivisors

on sumList(listOfNumbers)

script o

property l : listOfNumbers

end script

set sum to 0

repeat with n in o's l

set sum to sum + n

end repeat

return sum

end sumList

on amicablePairsBelow(limitPlus1)

script o

property pdSums : {missing value} -- Sums of proper divisors. (Dummy item for 1's.)

end script

set limit to limitPlus1 - 1

repeat with n from 2 to limit

set end of o's pdSums to sumList(properDivisors(n))

end repeat

set output to {}

repeat with n1 from 2 to (limit - 1)

set n2 to o's pdSums's item n1

if ((n1 < n2) and (n2 < limitPlus1) and (o's pdSums's item n2 = n1)) then ¬

set end of output to {n1, n2}

end repeat

return output

end amicablePairsBelow

on join(lst, delim)

set astid to AppleScript's text item delimiters

set AppleScript's text item delimiters to delim

set txt to lst as text

set AppleScript's text item delimiters to astid

return txt

end join

on task()

set output to amicablePairsBelow(20000)

repeat with thisPair in output

set thisPair's contents to join(thisPair, " & ")

end repeat

return join(output, linefeed)

end task

task()</syntaxhighlight>

{{output}}

<syntaxhighlight lang="applescript">"220 & 284

1184 & 1210

2620 & 2924

5020 & 5564

6232 & 6368

10744 & 10856

12285 & 14595

17296 & 18416"</syntaxhighlight>