AoC 2015.5 p1+2

1 files changed, 73 insertions, 0 deletions

diff --git a/doesnt-he-have-intern-elves-for-this/dhhieft.scm b/doesnt-he-have-intern-elves-for-this/dhhieft.scm
new file mode 100644
index 0000000..b2b9552
--- /dev/null
+++ b/doesnt-he-have-intern-elves-for-this/dhhieft.scm
@@ -0,0 +1,73 @@
+(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))