Max Range Sum

昨日に引き続き CodeEval から。

　cf. Max Range Sum – CodeEval

(define slices
  (lambda (lis n)
    (let loop ((l1 lis) (l2 '()))
      (if (< (length l1) n)
          (reverse l2)
          (loop (cdr l1)
            (cons (take l1 n) l2))))))

(define sum
  (lambda (lis)
    (apply + lis)))

(define solv
  (lambda (str)
    (let* ((s (string-split str ";"))
           (n (string->number (car s)))
           (lis (map string->number (string-split (cadr s) " "))))
      (apply max (cons 0 (map sum (slices lis n)))))))

(define print-solv
  (lambda (str)
    (print (solv str))))

(define main
  (lambda (args)
    (with-input-from-file (cadr args)
      (lambda ()
        (port-for-each print-solv read-line)))))

takatoh@nightschool $ cat input.txt
5;7 -3 -10 4 2 8 -2 4 -5 -2
6;-4 3 -10 5 3 -7 -3 7 -6 3
3;-7 0 -45 34 -24 7
takatoh@nightschool $ gosh max_range_sum.scm input.txt
16
0
17