newlispfanclub.alh.net

Code: Select all

(define (find-number lst)
	(define Myhash:Myhash)  ; hash table creation, O(1) lookup time
	(set ' total 0)
	(dolist (n lst)
	(if (Myhash n)
		(dec total n)    ; decrease when already added before
		(begin 
			(Myhash n true)
			(inc total n))))  ; if not in hash table increase
	(delete 'Myhash)  ; first to delete contents and namespace
	(delete 'Myhash)  ; second to delete symbol
	total)

(find-number '(1 2 3 4 5 3 2 1 5))

-> 4

Code: Select all

(define (find-number lst) (apply ^ lst))
(find-number '(1 3 1 2 3 4 5 2 4))
;-> 5