Project Euler Problem 4

Problem 4

Scheme

(use srfi-1)
(use srfi-42)
(use numbers)

(define (number->list n)
  (define (body n)
    (if (zero? n) '()
        (cons (modulo n 10) (body (floor (/ n 10))))))
  (if (zero? n) '(0)
      (reverse (body n))))

(define (palindrome? n)
  (let ((ls (number->list n)))
    (equal? ls (reverse ls))))

(define (p004)
  (print (max-ec (: i 100 1000) (: j i 1000) (:let n (* i j))
                 (if (palindrome? n)) n)))

(p004)

C++

#include <cstdio>
#include <algorithm>
using namespace std;

bool is_palindrome(int n)
{
    int rev = 0, buf = n;
    do {
        rev = 10*rev + buf%10;
        buf /= 10;
    } while(buf != 0);
    return rev == n;
}

int main()
{
    int ma = 0;
    for (int i = 100; i < 1000; i++) {
        for (int j = i; j < 1000; j++) {
            int t = i*j;
            if (is_palindrome(t))
                ma = max(ma, t);
        }
    }
    printf("%d\n", ma);
    return 0;
}