day 4: number intervals overlap

day4-id-intervals.lisp

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+;;; https://adventofcode.com/2022/day/4
+
+;; so, just read two intervals.
+;; intervals , separated, two numbers - separated.
+;; so. ugh. have a parsing function. maybe ask how to better parse
+;; then to calculate "total inclusion" - can go both ways, so 4 checks
+
+(setq test-line "2-4,6-8")
+(setq test-line "2-8,3-7")
+
+(require 'cl-ppcre)
+;; (cl-ppcre:split "(\\ )" line :with-registers-p nil)
+(setq intervals (mapcar #'parse-integer (cl-ppcre:split "(,|-)" test-line)))
+
+(defun line-to-nums (line)
+  (mapcar #'parse-integer (cl-ppcre:split "(,|-)" line)))
+
+(defun first-includes-second (l1 r1 l2 r2)
+  (and (<= l1 l2) (>= r1 r2)))
+
+(first-includes-second 2 8 3 7)
+(first-includes-second 3 8 3 7)
+(first-includes-second 4 8 3 7)
+
+(defun first-or-last-includes-another (l1 r1 l2 r2)
+  (or (first-includes-second l1 r1 l2 r2)
+      (first-includes-second l2 r2 l1 r1)))
+
+(with-open-file (in-file "day4-test-input.txt")
+  (let ((running-count 0))
+    (loop
+      for line = (read-line in-file nil nil)
+      while line
+      do (if (apply #'first-or-last-includes-another (line-to-nums line))
+             (incf running-count 1))
+      finally (return running-count))))
+
+(defun count-full-interlaps (filename)
+  (with-open-file (in-file filename)
+  (let ((running-count 0))
+    (loop
+      for line = (read-line in-file nil nil)
+      while line
+      do (if (apply #'first-or-last-includes-another (line-to-nums line))
+             (incf running-count 1))
+      finally (return running-count)))))
+
+(count-full-interlaps "day4-test-input.txt")
+(count-full-interlaps "day4-input.txt")
+
+;; next part - count intervals that "overlap at all", even if by single point
+;; could count 'not overlapping' - should be very easy
+;; and count total, and deduct
+
+(defun count-any-overlap (filename)
+  (with-open-file (in-file filename)
+  (let ((running-count-non-overlap 0)
+        (total-count 0))
+    (loop
+      for line = (read-line in-file nil nil)
+      while line
+      do (let ((nums (line-to-nums line)))
+           (if (or (< (second nums) (third nums))
+                   (< (fourth nums) (first nums)))
+               (incf running-count-non-overlap 1))
+           (incf total-count 1)
+           )
+      finally (return (- total-count running-count-non-overlap))))))
+
+(count-any-overlap "day4-test-input.txt")
+(count-any-overlap "day4-input.txt")

day4-test-input.txt

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+2-4,6-8
+2-3,4-5
+5-7,7-9
+2-8,3-7
+6-6,4-6
+2-6,4-8