paiza「水着」ゲットチャレンジ！ をCommonLispで解いてみた．

paiza-ando13.lisp

(defun get-input ()
  (parse-integer (read-line)))

(defun factorial (n)
  (if (<= n 1)
    1
    (* n (factorial (1- n)))))

(defun trim-zero-right (s)
  (if (eq (elt s (1- (length s))) #\0)
    (trim-zero-right (subseq s 0 (1- (length s))))
    s))

(defun nine-tail (s)
  (if (<= (length s) 9)
    s
    (subseq s (- (length s) 9) (length s))))

(defun trim-zero-left (s)
  (if (eq (elt s 0) #\0)
    (trim-zero-left (subseq s 1 (length s)))
    s))

(defun main ()
  (princ (trim-zero-left
           (nine-tail
             (trim-zero-right
               (write-to-string
                 (factorial (get-input))))))))