Project Euler Problem 3

Problem 3

Scheme

(use srfi-1)

(define (prime-factors n)
  (if (= n 1) '()
      (let loop ((d 2))
        (if (zero? (modulo n d)) (cons d (prime-factors (/ n d)))
            (loop (+ d 1))))))

(define (p003)
  (print (apply max (prime-factors 600851475143))))

(p003)

C++

#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long ll;

ll lpf(ll n)
{
    if (n == 1)
        return 1;
    for (ll d = 2;; d++)
        if (n%d==0)
            return max(d, lpf(n/d));
}

int main()
{
    printf("%lld\n", lpf(600851475143));
    return 0;
}