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(define-module (dhhieft)
#:use-module (srfi srfi-1)
#:export (dhhieft
string->vowels
three-vowels?
repeated-char?
favorable-string?
long-distance-match?))
(define (dhhieft str p2?)
(count (lambda (x) x)
(map (lambda (str)
(favorable-string? str p2?))
(string-split
(string-trim-both str char-set:whitespace)
#\newline))))
(define (favorable-string? str p2?)
"Returns #t or #f depending on if STR
meets the requirements defined in the problem
definition.
If p2? is true, uses the problem two definition
of favorable."
(let ((gap (if p2? 1 0)))
(and (repeated-char? str gap)
(if p2?
(long-distance-match? str)
(and (three-vowels? str)
(not (or (string-contains str "ab")
(string-contains str "cd")
(string-contains str "pq")
(string-contains str "xy"))))))))
(define (long-distance-match? str)
"Given STR, returns #t if a substring
of size two is repeated multiple times in
STR, non-overlapping."
(if (< (string-length str) 3)
#f
(let loop ((str (substring str 2)) (pair (substring str 0 2)))
(cond
((string-contains str pair) #t)
((< (string-length str) 3) #f)
(#t (loop (substring str 1)
(string-append (substring pair 1) (substring str 0 1))))))))
(define (repeated-char? str gapsize)
"Given STR, returns a boolean
indicating if the string contains
a repeated character.
GAPSIZE is the number of characters to
skip when making repeated char comparisons."
(let loop ((lst (string->list str)))
(cond
((>= (1+ gapsize) (length lst)) #f)
((equal? (car lst) (list-ref lst (1+ gapsize))) #t)
(#t (loop (cdr lst))))))
(define (three-vowels? str)
"Given STR, returns a boolean
indicating if the string contains
at least three vowels."
(>= (string-length
(string->vowels (string-downcase str)))
3))
(define (string->vowels str)
"Given STR, returns STR with all
non-vowel characters removed."
(string-filter (char-set #\a #\e #\i #\o #\u) str))
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