Euler Project 38

Take the number 192 and multiply it by each of 1, 2, and 3:

192  1 = 192
192  2 = 384
192  3 = 576

By concatenating each product we get the 1 to 9 pandigital, 192384576. We will call 192384576 the concatenated product of 192 and (1,2,3)

The same can be achieved by starting with 9 and multiplying by 1, 2, 3, 4, and 5, giving the pandigital, 918273645, which is the concatenated product of 9 and (1,2,3,4,5).

What is the largest 1 to 9 pandigital 9-digit number that can be formed as the concatenated product of an integer with (1,2, ... , n) where n  1?

My Solution

(defun IsPandigital(n)

  (let ((IsPandigitalNum T))

    (loop for i from 1 to 9

         do(if (null (position (format nil "~a" i) n :test #'string=))

                (progn (setq IsPandigitalNum nil)

                (return IsPandigitalNum))))

   IsPandigitalNum))

(defun Eluer38()

  (let ((currentPandigital "")

         (tempstr "")

         (tempPandigital "")

         (currentnumber 0))

    (loop for i from 1 to 10000

         do(progn (loop for j from 1 to 9

                        do(progn (setq tempstr (concatenate 'string

                                                                           tempstr

                                                                           (format nil "~a" (* i j))))

                     (if (= 9 (length tempstr))

                         (setq tempPandigital tempstr))))

                     (if (IsPandigital tempPandigital)

                         (progn (if (> (parse-integer tempPandigital) currentnumber)

                         (setq currentnumber (parse-integer tempPandigital)))))

                      (setq tempPandigital "")

                      (setq tempstr "")))

   currentnumber))