Largest prime factor: Difference between revisions
Added Easylang |
Initial FB submission for Largest prime factor |
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=={{header|FutureBasic}}== |
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<syntaxhighlight lang="futurebasic"> |
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include "NSLog.incl" |
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local fn LargestPrimeFactor( numToFactor as UInt64 ) |
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UInt64 latestDivisor = 2 |
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while ( numToFactor != 1 ) |
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latestDivisor = 2 |
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while ( numToFactor % latestDivisor != 0 ) |
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latestDivisor += 1 |
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wend |
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numToFactor /= latestDivisor |
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wend |
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NSLog( @"%lld", latestDivisor ) |
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end fn |
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fn LargestPrimeFactor( 600851475143 ) |
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HandleEvents |
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</syntaxhighlight> |
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{{output}} |
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<pre> |
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6857 |
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</pre> |
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=={{header|Go}}== |
=={{header|Go}}== |
Revision as of 00:46, 14 July 2024
- Task
The task description is taken for Project Euler (https://projecteuler.net/problem=3)
What is the largest prime factor of the number 600851475143 ?
11l
F isPrime(n)
L(i) 2 .. Int(n ^ 0.5)
I n % i == 0
R 0B
R 1B
V n = 600851475143
V j = 3
L !isPrime(n)
I n % j == 0
n I/= j
j += 2
print(n)
- Output:
6857
ALGOL 68
Based on the Wren and Go samples.
BEGIN # find the largest prime factor of a number #
# returns the largest prime factor of n #
PROC max prime factor = ( LONG INT n )LONG INT:
IF n < 2
THEN 1
ELSE
LONG INT max factor := n;
# even factors - only 2 is prime #
LONG INT v := n;
WHILE NOT ODD v DO
max factor := 2;
v OVERAB 2
OD;
# odd factors #
LONG INT k := 3;
LONG INT root n = ENTIER long sqrt( n );
WHILE k <= root n AND v > 1 DO
WHILE v MOD k = 0 AND v > 1 DO
max factor := k;
v OVERAB k
OD;
k +:= 2
OD;
IF v > 1 THEN v ELSE max factor FI
FI # max prime factor # ;
# test the max prime factor routine #
PROC test = ( LONG INT n )VOID:
print( ( "Largest prime factor of ", whole( n, 0 ), " is ", whole( max prime factor( n ), 0 ), newline ) );
# test cases #
test( 600 851 475 143 );
test( 6 008 );
test( 751 )
END
- Output:
Largest prime factor of 600851475143 is 6857 Largest prime factor of 6008 is 751 Largest prime factor of 751 is 751
Arturo
print max factors.prime 600851475143
- Output:
6857
AutoHotkey
MsgBox % result := max(prime_numbers(600851475143)*)
prime_numbers(n) {
if (n <= 3)
return [n]
ans := [], done := false
while !done {
if !Mod(n,2)
ans.push(2), n /= 2
else if !Mod(n,3)
ans.push(3), n /= 3
else if (n = 1)
return ans
else {
sr := sqrt(n), done := true, i := 6
while (i <= sr+6) {
if !Mod(n, i-1) ; is n divisible by i-1?
ans.push(i-1), n /= i-1, done := false
if !Mod(n, i+1) ; is n divisible by i+1?
ans.push(i+1), n /= i+1, done := false
if !done
break
i+=6
}}}
ans.push(Format("{:d}", n))
return ans
}
- Output:
6857
AWK
# syntax: GAWK -f LARGEST_PRIME_FACTOR.AWK
# converted from FreeBASIC
BEGIN {
N = n = "600851475143"
j = 3
while (!is_prime(n)) {
if (n % j == 0) {
n /= j
}
j += 2
}
printf("The largest prime factor of %s is %d\n",N,n)
exit(0)
}
function is_prime(x, i) {
if (x <= 1) {
return(0)
}
for (i=2; i<=int(sqrt(x)); i++) {
if (x % i == 0) {
return(0)
}
}
return(1)
}
- Output:
The largest prime factor of 600851475143 is 6857
BASIC
Applesoft BASIC
Código sacado de https://www.calormen.com/jsbasic/ El código original es de Christiano Trabuio.
100 HOME
110 LET a = 600851475143
120 LET f = 0
130 IF a/2 = INT(a/2) THEN LET a = a/2: LET f = 1: GOTO 130
140 LET i = 3
150 LET e = INT(SQR(a)) + 2
160 LET f = 0
170 FOR n = i TO e STEP 2
180 IF a /n = INT(a/n) THEN LET a = a / n: LET i = n: LET n = e: LET f = 1
190 NEXT n
200 IF a > n AND f <> 0 THEN GOTO 160
210 PRINT a
220 END
- Output:
6857
BASIC256
#No primality testing is even required.
n = 600851475143
j = 3
do
if int(n/j) = n/j then n /= j
j += 2
until j = n
print n
- Output:
6857
Chipmunk Basic
100 CLS : REM 10 HOME para Applesoft BASIC
110 LET a = 600851475143
120 LET f = 0
130 IF a/2 = INT(a/2) THEN LET a = a/2: LET f = 1: GOTO 130
140 LET i = 3
150 LET e = INT(SQR(a)) + 2
160 LET f = 0
170 FOR n = i TO e STEP 2
180 IF a /n = INT(a/n) THEN LET a = a / n: LET i = n: LET n = e: LET f = 1
190 NEXT n
200 IF a > n AND f <> 0 THEN GOTO 160
210 PRINT a
220 END
- Output:
6857
FreeBASIC
#include"isprime.bas"
dim as ulongint n = 600851475143, j = 3
while not isprime(n)
if n mod j = 0 then n/=j
j+=2
wend
print n
- Output:
6857
GW-BASIC
No primality testing is even required.
10 N#=600851475143#
20 J#=3
30 IF J#=N# THEN GOTO 100
40 IF INT(N#/J#) = N#/J# THEN N# = N#/J#
50 J#=J#+2
60 GOTO 30
100 PRINT N#
- Output:
6857
QBasic
REM No primality testing is even required.
DIM a AS DOUBLE
a = 600851475143#
i = 3
DO
IF INT(a / i) = a / i THEN a = a / i
i = i + 2
LOOP UNTIL a = i ' o WHILE a <> i
PRINT a
- Output:
6857
Run BASIC
function isPrime(n)
if n < 2 then isPrime = 0 : goto [exit]
if n = 2 then isPrime = 1 : goto [exit]
if n mod 2 = 0 then isPrime = 0 : goto [exit]
isPrime = 1
for i = 3 to int(n^.5) step 2
if n mod i = 0 then isPrime = 0 : goto [exit]
next i
[exit]
end function
n = 600851475143
j = 3
while isPrime(n) <> 1
if n mod j = 0 then n = n / j
j = j +2
wend
print n
'But, no primality testing is even required.
n = 600851475143
j = 3
while j <> n
if int(n/j) = n / j then n = n / j
j = j +2
wend
print n
end
- Output:
6857 6857
True BASIC
!No primality testing is even required.
LET n = 600851475143
LET j = 3
DO WHILE j <> n
IF INT(n/j) = n / j THEN LET n = n / j
LET j = j + 2
LOOP
PRINT n
END
- Output:
6857
XBasic
PROGRAM "LPF"
VERSION "0.0000"
DECLARE FUNCTION Entry ()
FUNCTION Entry ()
'No primality testing is even required.
DOUBLE n
n = 600851475143
j = 3
DO
IF INT(n/j) = n/j THEN n = n / j
j = j + 2
LOOP UNTIL j = n
PRINT n
END FUNCTION
END PROGRAM
- Output:
6857
Yabasic
//No primality testing is even required.
n = 600851475143
j = 3
repeat
if int(n/j) = n/j n = n / j
j = j + 2
until j = n
print n
- Output:
6857
BCPL
This version creates a 2,3,5 wheel object, which is instantiated by the factorization routine.
GET "libhdr"
LET new_235wheel() = VALOF {
LET w = getvec(1)
w!0 := 1 // accumulator
w!1 := -3 // index (negative => first few primes)
RESULTIS w
}
LET next235(w) = VALOF {
LET p3 = TABLE 2, 3, 5
LET wheel235 = TABLE 6, 4, 2, 4, 2, 4, 6, 2
LET a, i = w!0, w!1
TEST i < 0
THEN {
a := p3[i + 3]
i +:= 1
}
ELSE {
a +:= wheel235[i]
i := (i + 1) & 7
w!0 := a
}
w!1 := i
RESULTIS a
}
LET gpf(n) = VALOF {
LET w = new_235wheel()
LET d = next235(w)
UNTIL d*d > n {
TEST n MOD d = 0
THEN n /:= d
ELSE d := next235(w)
}
freevec(w)
RESULTIS n
}
LET start() = VALOF {
writef("The largest prime factor of 600,851,475,143 is %d *n", gpf(600_851_475_143))
RESULTIS 0
}
- Output:
BCPL 64-bit Cintcode System (13 Jan 2020) 0.000> The largest prime factor of 600,851,475,143 is 6857 0.001>
C
#include <stdio.h>
#include <stdlib.h>
int isprime( long int n ) {
int i=3;
if(!(n%2)) return 0;
while( i*i < n ) {
if(!(n%i)) return 0;
i+=2;
}
return 1;
}
int main(void) {
long int n=600851475143, j=3;
while(!isprime(n)) {
if(!(n%j)) n/=j;
j+=2;
}
printf( "%ld\n", n );
return 0;
}
- Output:
6857
CoffeeScript
wheel235 = () ->
yield 2
yield 3
yield 5
a = 1
i = 0
wheel = [6, 4, 2, 4, 2, 4, 6, 2]
loop
a += wheel[i]
yield a
i = (i + 1) & 7
gpf = (n) ->
w = wheel235()
d = w.next().value
until d*d > n
if n % d is 0
n //= d
else
d = w.next().value
n
console.log "The largest prime factor of 600,851,475,143 is #{gpf(600_851_475_143)}"
- Output:
The largest prime factor of 600,851,475,143 is 6857
Delphi
function IsPrime(N: int64): boolean;
{Fast, optimised prime test}
var I,Stop: int64;
begin
if (N = 2) or (N=3) then Result:=true
else if (n <= 1) or ((n mod 2) = 0) or ((n mod 3) = 0) then Result:= false
else
begin
I:=5;
Stop:=Trunc(sqrt(N+0.0));
Result:=False;
while I<=Stop do
begin
if ((N mod I) = 0) or ((N mod (I + 2)) = 0) then exit;
Inc(I,6);
end;
Result:=True;
end;
end;
function GetLargestPrimeFact(N: int64): int64;
var J: int64;
begin
J:=3;
while not IsPrime(N) do
begin
if (N mod j) = 0 then N:=N div J;
Inc(J,2);
end;
Result:=N;
end;
procedure TestLargePrimeFact(Memo: TMemo);
var F: integer;
begin
F:=GetLargestPrimeFact(600851475143);
Memo.Lines.Add(IntToStr(F));
end;
- Output:
6857
EasyLang
n = 600851475143
i = 2
while n > i
if n mod i = 0
n = n div i
.
i += 1
.
print n
- Output:
6857
Elixir
defmodule Factor do
def wheel235(), do:
Stream.concat(
[2, 3, 5],
Stream.scan(Stream.cycle([6, 4, 2, 4, 2, 4, 6, 2]), 1, &+/2)
)
def gpf(n), do: gpf n, wheel235()
defp gpf(n, divs) do
[d] = Enum.take divs, 1
cond do
d*d > n -> n
rem(n, d) === 0 -> gpf div(n, d), divs
true -> gpf n, Stream.drop(divs, 1)
end
end
end
IO.puts "The largest prime factor of 600,851,475,143 is #{Factor.gpf(600_851_475_143)}"
- Output:
The largest prime factor of 600,851,475,143 is 6857
Erlang
Uses a factorization wheel, but without builtin lazy lists, it's rather awkward for a functional language.
main(_) ->
test(),
io:format("The largest prime factor of 600,851,475,143 is ~w~n", [gpf(600851475143)]).
gpf(N) -> gpf(N, 2, 0, <<1, 2, 2, 4, 2, 4, 2, 4, 6, 2, 6>>).
gpf(N, D, J, Wheel) when J =:= byte_size(Wheel) -> gpf(N, D, 3, Wheel);
gpf(N, D, _, _) when D*D > N -> N;
gpf(N, D, J, Wheel) when N rem D =:= 0 -> gpf(N div D, D, J, Wheel);
gpf(N, D, J, Wheel) -> gpf(N, D + binary:at(Wheel, J), J + 1, Wheel).
test() ->
3 = gpf(27),
5 = gpf(125),
7 = gpf(98),
101 = gpf(101),
23 = gpf(23 * 13).
- Output:
The largest prime factor of 600,851,475,143 is 6857
F#
printfn "%d" (Seq.last<|Open.Numeric.Primes.Prime.Factors 600851475143L)
- Output:
6857
Factor
USING: math.primes.factors prettyprint sequences ;
600851475143 factors last .
Fermat
n:=600851475143;
j:=3;
while Isprime(n)<>1 do
if Divides(j, n) then n:=n/j fi;
j:=j+2;
od;
!!n;
- Output:
6857
FutureBasic
include "NSLog.incl"
local fn LargestPrimeFactor( numToFactor as UInt64 )
UInt64 latestDivisor = 2
while ( numToFactor != 1 )
latestDivisor = 2
while ( numToFactor % latestDivisor != 0 )
latestDivisor += 1
wend
numToFactor /= latestDivisor
wend
NSLog( @"%lld", latestDivisor )
end fn
fn LargestPrimeFactor( 600851475143 )
HandleEvents
- Output:
6857
Go
package main
import "fmt"
func largestPrimeFactor(n uint64) uint64 {
if n < 2 {
return 1
}
inc := [8]uint64{4, 2, 4, 2, 4, 6, 2, 6}
max := uint64(1)
for n%2 == 0 {
max = 2
n /= 2
}
for n%3 == 0 {
max = 3
n /= 3
}
for n%5 == 0 {
max = 5
n /= 5
}
k := uint64(7)
i := 0
for k*k <= n {
if n%k == 0 {
max = k
n /= k
} else {
k += inc[i]
i = (i + 1) % 8
}
}
if n > 1 {
return n
}
return max
}
func main() {
n := uint64(600851475143)
fmt.Println("The largest prime factor of", n, "is", largestPrimeFactor(n), "\b.")
}
- Output:
The largest prime factor of 600851475143 is 6857.
J
{:q:600851475143
6857
jq
Works with gojq, the Go implementation of jq
Using `factors` as defined at Prime_decomposition#jq:
600851475143 | last(factors)
- Output:
6857
Julia
using Primes
@show first(last(factor(600851475143).pe))
- Output:
first(last((factor(600851475143)).pe)) = 6857
Mathematica / Wolfram Language
Max[FactorInteger[600851475143][[All, 1]]]
- Output:
6857
PARI/GP
A=factor(600851475143)
print(A[matsize(A)[1],1])
- Output:
6857
Perl
use strict;
use warnings;
use feature 'say';
sub f {
my($n) = @_;
$n % $_ or return $_, f($n/$_) for 2..$n
}
say +(f 600851475143)[-2]
- Output:
6857
Phix
with javascript_semantics ?prime_factors(600851475143,false,-1)[$]
- Output:
6857
PL/I
Based on the Wren, Go and Algol 68 samples.
/* find the largest prime factor of 600851475143 */
largestPrimeFactor: procedure options( main );
declare ( n, maxFactor, v, k, rootN ) decimal( 12 )fixed;
n = 600851475143;
maxFactor = n;
/* even factors */
v = n;
do while( mod( v, 2 ) = 0 );
maxFactor = 2;
v = v / 2;
end;
/* odd factors */
k = 3;
rootN = sqrt( n );
do while( k <= rootN & v > 1 );
do while( mod( v, k ) = 0 & v > 1 );
maxFactor = k;
v = v / k;
end;
k = k + 2;
end;
if v > 1 then maxFactor = v;
put skip list( 'Largest prime factor of ', n, ' is ', maxFactor );
end largestPrimeFactor;
- Output:
Largest prime factor of 600851475143 is 6857
Prolog
wheel2357(L) :-
W = [2, 4, 2, 4, 6, 2, 6, 4,
2, 4, 6, 6, 2, 6, 4, 2,
6, 4, 6, 8, 4, 2, 4, 2,
4, 8, 6, 4, 6, 2, 4, 6,
2, 6, 6, 4, 2, 4, 6, 2,
6, 4, 2, 4, 2, 10, 2, 10 | W],
L = [1, 2, 2, 4 | W].
gpf(N, P) :- % greatest prime factor
wheel2357(W),
gpf(N, 2, W, P).
gpf(N, D, _, N) :- D*D > N, !.
gpf(N, D, W, X) :-
N mod D =:= 0, !,
N2 is N/D,
gpf(N2, D, W, X).
gpf(N, D, [S|Ss], X) :-
plus(D, S, D2),
gpf(N, D2, Ss, X).
main :-
gpf(600_851_475_143, Euler003),
format("The largest prime factor of 600,851,475,143 is ~p~n", [Euler003]),
halt.
?- main.
- Output:
The largest prime factor of 600,851,475,143 is 6857
Python
#!/usr/bin/python
def isPrime(n):
for i in range(2, int(n**0.5) + 1):
if n % i == 0:
return False
return True
if __name__ == '__main__':
n = 600851475143
j = 3
while not isPrime(n):
if n % j == 0:
n /= j
j += 2
print(n);
Quackery
primefactors
is defined at Prime decomposition#Quackery.
600851475143 primefactors -1 peek echo
- Output:
6857
R
First uses the Sieve of Eratosthenes to find possible factors then tests each possible prime p for divisibility and also n/p.
sieve <- function(n) {
if (n < 2)
return (NULL)
primes <- rep(TRUE, n)
primes[1] <- FALSE
for (i in 1:floor(sqrt(n)))
if (primes[i])
primes[seq(i*i, n, by = i)] <- FALSE
which(primes)
}
prime.factors <- function(n) {
primes <- sieve(floor(sqrt(n)))
factors <- primes[n %% primes == 0]
if (length(factors) == 0)
n
else {
for (p in factors) { # add all elements of n/p that are also prime
d <- n / p
if (d != p && all(d %% primes[primes <= floor(sqrt(d))] != 0))
factors <- c(factors, d)
}
factors
}
}
cat("The prime factors of 600,851,475,143 are", paste(prime.factors(600851475143), collapse = ", "), "\n")
- Output:
The prime factors of 600,851,475,143 are 71, 839, 1471, 6857
Raku
Note: These are both extreme overkill for the task requirements.
Not particularly fast
Pure Raku. Using Prime::Factor from the Raku ecosystem. Makes it to 2^95 - 1 in 1 second on my system.
use Prime::Factor;
my $start = now;
for flat 600851475143, (1..∞).map: { 2 +< $_ - 1 } {
say "Largest prime factor of $_: ", max prime-factors $_;
last if now - $start > 1; # quit after one second of total run time
}
Largest prime factor of 600851475143: 6857 Largest prime factor of 3: 3 Largest prime factor of 7: 7 Largest prime factor of 15: 5 Largest prime factor of 31: 31 Largest prime factor of 63: 7 Largest prime factor of 127: 127 Largest prime factor of 255: 17 Largest prime factor of 511: 73 Largest prime factor of 1023: 31 Largest prime factor of 2047: 89 Largest prime factor of 4095: 13 Largest prime factor of 8191: 8191 Largest prime factor of 16383: 127 Largest prime factor of 32767: 151 Largest prime factor of 65535: 257 Largest prime factor of 131071: 131071 Largest prime factor of 262143: 73 Largest prime factor of 524287: 524287 Largest prime factor of 1048575: 41 Largest prime factor of 2097151: 337 Largest prime factor of 4194303: 683 Largest prime factor of 8388607: 178481 Largest prime factor of 16777215: 241 Largest prime factor of 33554431: 1801 Largest prime factor of 67108863: 8191 Largest prime factor of 134217727: 262657 Largest prime factor of 268435455: 127 Largest prime factor of 536870911: 2089 Largest prime factor of 1073741823: 331 Largest prime factor of 2147483647: 2147483647 Largest prime factor of 4294967295: 65537 Largest prime factor of 8589934591: 599479 Largest prime factor of 17179869183: 131071 Largest prime factor of 34359738367: 122921 Largest prime factor of 68719476735: 109 Largest prime factor of 137438953471: 616318177 Largest prime factor of 274877906943: 524287 Largest prime factor of 549755813887: 121369 Largest prime factor of 1099511627775: 61681 Largest prime factor of 2199023255551: 164511353 Largest prime factor of 4398046511103: 5419 Largest prime factor of 8796093022207: 2099863 Largest prime factor of 17592186044415: 2113 Largest prime factor of 35184372088831: 23311 Largest prime factor of 70368744177663: 2796203 Largest prime factor of 140737488355327: 13264529 Largest prime factor of 281474976710655: 673 Largest prime factor of 562949953421311: 4432676798593 Largest prime factor of 1125899906842623: 4051 Largest prime factor of 2251799813685247: 131071 Largest prime factor of 4503599627370495: 8191 Largest prime factor of 9007199254740991: 20394401 Largest prime factor of 18014398509481983: 262657 Largest prime factor of 36028797018963967: 201961 Largest prime factor of 72057594037927935: 15790321 Largest prime factor of 144115188075855871: 1212847 Largest prime factor of 288230376151711743: 3033169 Largest prime factor of 576460752303423487: 3203431780337 Largest prime factor of 1152921504606846975: 1321 Largest prime factor of 2305843009213693951: 2305843009213693951 Largest prime factor of 4611686018427387903: 2147483647 Largest prime factor of 9223372036854775807: 649657 Largest prime factor of 18446744073709551615: 6700417 Largest prime factor of 36893488147419103231: 145295143558111 Largest prime factor of 73786976294838206463: 599479 Largest prime factor of 147573952589676412927: 761838257287 Largest prime factor of 295147905179352825855: 131071 Largest prime factor of 590295810358705651711: 10052678938039 Largest prime factor of 1180591620717411303423: 122921 Largest prime factor of 2361183241434822606847: 212885833 Largest prime factor of 4722366482869645213695: 38737 Largest prime factor of 9444732965739290427391: 9361973132609 Largest prime factor of 18889465931478580854783: 616318177 Largest prime factor of 37778931862957161709567: 10567201 Largest prime factor of 75557863725914323419135: 525313 Largest prime factor of 151115727451828646838271: 581283643249112959 Largest prime factor of 302231454903657293676543: 22366891 Largest prime factor of 604462909807314587353087: 1113491139767 Largest prime factor of 1208925819614629174706175: 4278255361 Largest prime factor of 2417851639229258349412351: 97685839 Largest prime factor of 4835703278458516698824703: 8831418697 Largest prime factor of 9671406556917033397649407: 57912614113275649087721 Largest prime factor of 19342813113834066795298815: 14449 Largest prime factor of 38685626227668133590597631: 9520972806333758431 Largest prime factor of 77371252455336267181195263: 2932031007403 Largest prime factor of 154742504910672534362390527: 9857737155463 Largest prime factor of 309485009821345068724781055: 2931542417 Largest prime factor of 618970019642690137449562111: 618970019642690137449562111 Largest prime factor of 1237940039285380274899124223: 18837001 Largest prime factor of 2475880078570760549798248447: 23140471537 Largest prime factor of 4951760157141521099596496895: 2796203 Largest prime factor of 9903520314283042199192993791: 658812288653553079 Largest prime factor of 19807040628566084398385987583: 165768537521 Largest prime factor of 39614081257132168796771975167: 30327152671
Particularly fast
Using Perl 5 ntheory library via Inline::Perl5. Makes it to about 2^155 - 1 in 1 second on my system. Varies from 2^145-1 (lowest seen) to 2^168-1 (highest seen).
use Inline::Perl5;
my $p5 = Inline::Perl5.new();
$p5.use: 'ntheory';
my &lpf = $p5.run('sub { ntheory::todigitstring ntheory::vecmax ntheory::factor $_[0] }');
my $start = now;
for flat 600851475143, (1..∞).map: { 2 +< $_ - 1 } {
say "Largest prime factor of $_: ", lpf "$_";
last if now - $start > 1; # quit after one second of total run time
}
Same output only much longer.
Ring
load "stdlib.ring"
see "working..." + nl
see "The largest prime factor of the number 600851475143 is:" + nl
num = 600851475143
numSqrt = sqrt(num)
numSqrt = floor(numSqrt)
if numSqrt%2 = 0
numSqrt++
ok
for n = numSqrt to 3 step -2
if isprime(n) and num%n = 0
exit
ok
next
see "" + n + nl
see "done..." + nl
- Output:
working... The largest prime factor of the number 600851475143 is: 6857 done...
RPL
The task can be solved directly by a command line:
600851475143 FACTORS 1 GET
- Output:
1: 6857
Ruby
require 'prime'
p 600851475143.prime_division.last.first
- Output:
6857
Rust
fn main( ) {
let mut current : i64 = 600851475143 ;
let mut latest_divisor : i64 = 2 ;
while current != 1 {
latest_divisor = 2 ;
while current % latest_divisor != 0 {
latest_divisor += 1 ;
}
current /= latest_divisor ;
}
println!("{}" , latest_divisor ) ;
}
- Output:
6857
Sidef
var n = 600851475143
say gpf(n) #=> 6857
say factor(n).last #=> 6857
Wren
Without using any library functions at all (it's a one-liner otherwise):
var largestPrimeFactor = Fn.new { |n|
if (!n.isInteger || n < 2) return 1
var inc = [4, 2, 4, 2, 4, 6, 2, 6]
var max = 1
while (n%2 == 0) {
max = 2
n = (n/2).floor
}
while (n%3 == 0) {
max = 3
n = (n/3).floor
}
while (n%5 == 0) {
max = 5
n = (n/5).floor
}
var k = 7
var i = 0
while (k * k <= n) {
if (n%k == 0) {
max = k
n = (n/k).floor
} else {
k = k + inc[i]
i = (i + 1) % 8
}
}
return (n > 1) ? n : max
}
var n = 600851475143
System.print("The largest prime factor of %(n) is %(largestPrimeFactor.call(n)).")
- Output:
The largest prime factor of 600851475143 is 6857.
XPL0
real Num, Max, Div, Quot;
[Num:= 600851475143.;
Max:= 0.;
Div:= 2.;
repeat loop [Quot:= Num / Div;
if Mod(Quot, 1.) < 1E-10 then \evenly divisible
[Num:= Quot;
Max:= Div;
]
else quit;
if Div > Num then quit;
];
Div:= Div + 1.;
until Div > Num;
Format(1, 0);
RlOut(0, Max);
]
- Output:
6857
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