Smallest multiple
- Task
Task desciption is taken from Project Euler
(https://projecteuler.net/problem=5)
2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.
What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?
Pascal
Here the simplest way, like Raku, check the highest exponent of every prime in range
Using harded coded primes.
<lang pascal>{$IFDEF FPC}
{$MODE DELPHI}
{$ELSE}
{$APPTAYPE CONSOLE}
{$ENDIF} const
smallprimes : array[0..10] of Uint32 = (2,3,5,7,11,13,17,19,23,29,31); MAX = 20;
function getmaxfac(pr: Uint32): Uint32; //get the pr^highest exponent of prime used in 2 .. MAX var
i,fac : integer;
Begin
result := pr; while pr*result <= MAX do result *= pr;
end;
var
n,pr,prIdx : Uint32;
BEGIN
n := 1; prIdx := 0; pr := smallprimes[prIdx]; repeat pr := smallprimes[prIdx]; n *= getmaxfac(pr); inc(prIdx); pr := smallprimes[prIdx]; until pr>MAX; writeln(n);
{$IFDEF WINDOWS}
READLN;
{$ENDIF} END. </lang>
- Output:
232792560
Raku
Exercise with some larger values as well.
<lang perl6>use Prime::Factor;
sub minimum-multiple ($n where * > 1) {
my %max-factor; for 2..$n { .&prime-factors.Bag.map: { %max-factor{.key} max= .value } } [*] flat %max-factor.map: { .key xx .value }
}
say "$_: ", .&minimum-multiple for <10 20 200 2000>; printf "%.3f seconds elapsed\n", now - INIT now;</lang>
- Output:
10: 2520 20: 232792560 200: 337293588832926264639465766794841407432394382785157234228847021917234018060677390066992000 2000: 151117794877444315307536308337572822173736308853579339903227904473000476322347234655122160866668946941993951014270933512030194957221371956828843521568082173786251242333157830450435623211664308500316844478617809101158220672108895053508829266120497031742749376045929890296052805527212315382805219353316270742572401962035464878235703759464796806075131056520079836955770415021318508272982103736658633390411347759000563271226062182345964184167346918225243856348794013355418404695826256911622054015423611375261945905974225257659010379414787547681984112941581325198396634685659217861208771400322507388161967513719166366839894214040787733471287845629833993885413462225294548785581641804620417256563685280586511301918399010451347815776570842790738545306707750937624267501103840324470083425714138183905657667736579430274197734179172691637931540695631396056193786415805463680000 0.315 seconds elapsed
Ring
<lang ring> see "working..." + nl see "Smallest multiple is:" + nl n = 0
while true
n++ flag = 0 for m = 1 to 20 if n % m = 0 flag += 1 ok next if flag = 20 see "" + n + nl exit ok
end
see "done..." + nl </lang>
- Output:
working... Smallest multiple is: 232792560 done...