application/octet-stream
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749 B
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29 lines
;; The biggest product of 2 3-digit numbers that is a palindrome
;; https://projecteuler.net/problem=4
(require 'cl-lib)
(defun reverse-num (a)
(let ((ret 0))
(while (> a 0)
(progn (setf ret (+ (* ret 10) (mod a 10)))
(setf a (floor a 10))))
ret))
(defun palindrome? (a)
(eq a (reverse-num a)))
(defun start-search ()
(let ((max 0))
(dotimes (a 1000 max)
(dotimes (b 1000)
(let ((p (* a b)))
(when (and (palindrome? p)
(> p max))
(setf max p)))))))
(byte-compile 'reverse-num)
(byte-compile 'palindrome?)
(byte-compile 'start-search)
(princ (format "The biggest product of 2 3-digit numbers that is a palindrome is: %d\n" (start-search)))
