How Can I Improve This Algorithm (LCS)

Posted by superguay on Stack Overflow See other posts from Stack Overflow or by superguay
Published on 2010-04-08T05:38:37Z Indexed on 2010/04/08 5:43 UTC
Read the original article Hit count: 320

Filed under:

Scheme

(define (lcs lst1 lst2) (define (except-last-pair list) (if (pair? (cdr list)) (cons (car list) (except-last-pair (cdr list))) '())) (define (car-last-pair list) (if (pair? (cdr list)) (car-last-pair (cdr list)) (car list))) (if (or (null? lst1) (null? lst2)) null (if (= (car-last-pair lst1) (car-last-pair lst2)) (append (lcs (except-last-pair lst1) (except-last-pair lst2)) (cons (car-last-pair lst1) '())) **(if (> (length (lcs lst1 (except-last-pair lst2))) (length (lcs lst2 (except-last-pair lst1)))) (lcs lst1 (except-last-pair lst2)) (lcs lst2 (except-last-pair lst1))))))

I dont want it to run over and over..

Regards, Superguay

Related posts about Scheme

About "If.." in Scheme (plt-scheme)

as seen on Stack Overflow - Search for 'Stack Overflow'
I had a pretty simple requirement in my Scheme program to execute more than one statement, in the true condition of a 'if'. . So I write my code, something like this: (if (= 1 1) ((expression1) (expression2)) ; these 2 expressions are to be executed when the condition is true (expression3)… >>> More
Detecting EOF in a Binary File using Scheme

as seen on Stack Overflow - Search for 'Stack Overflow'
(define (read-all-input) (local ((define line (bytes->list (read-bytes 4)))) (if (eof-object? line) empty (cons line (read-all-input))))) (void (read-all-input)) The above code fails because bytes-list expects an argument of type byte string, but is given # >>> More
Scheme: Detecting duplicate elements in a list

as seen on Stack Overflow - Search for 'Stack Overflow'
Does R6RS or Chez Scheme v7.9.4 have a library function to check if a list contains duplicate elements? Alternatively, do either have any built in functionality for sets (which dis-allow duplicate elements)? So far, I've only been able to find an example here. The problem with that is that it doesn't… >>> More
Scheme implementations - what does it mean?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I'm a beginning student in CS, and my classes are mostly in Java. I'm currently going through "Little Schemer" as a self study, and in the process of finding out how to do that I have found numerous references to "implementations" of Scheme. My question is, what are implementations? Are they… >>> More
Traversing Scheme function as a list

as seen on Stack Overflow - Search for 'Stack Overflow'
Isn't it possible to treat functions in Scheme as any other list? Basically, what I want do to is something like this: (define (foo) "hello") (cdr foo) ; or similar, should return the list ((foo) "hello") I've found a similar discussion about this, and I feel a bit disappointed if this is not… >>> More

Developer IT