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  1. ; a fun little task
  2.  
  3. (define (insert lt? x xs)
  4.   (let loop ((xs xs) (zs (list)))
  5.     (cond ((null? xs) (reverse (cons x zs)))
  6.           ((lt? x (car xs))
  7.             (append (reverse zs) (list x) xs))
  8.           (else (loop (cdr xs) (cons (car xs) zs))))))
  9.  
  10. (define (remove x xs)
  11.   (let loop ((xs xs) (zs (list)))
  12.     (cond ((null? xs) (reverse zs))
  13.           ((equal? x (car xs))
  14.             (append (reverse zs) (cdr xs)))
  15.           (else (loop (cdr xs) (cons (car xs) zs))))))
  16.  
  17. (define (f a b)
  18.   (let* ((a-len (string-length a))
  19.          (b-len (string-length b))
  20.          (target (sort (string->list a) char<?))
  21.          (window (sort (string->list
  22.                    (substring b 0 a-len)) char<?)))
  23.     (let loop ((i 0) (j a-len) (window window))
  24.       (cond ((= j b-len) #f)
  25.             ((equal? target window) i)
  26.             (else (loop (+ i 1) (+ j 1)
  27.               (insert char<? (string-ref b j)
  28.                 (remove (string-ref b i) window))))))))
  29.  
  30. (display (f "xyz" "asdfgzyxpoiuy")) (newline) ; 5
  31. (display (f "wxyz" "asdfgzywpoiuy")) (newline) ; #f
Success #stdin #stdout 0.01s 42848KB
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5
#f
https://ideone.com/ERm8Tv
language:
Scheme (guile 2.2.4)
created:
7 years ago
visibility:
public

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