Day 5: If You Give A Seed A Fertilizer

chicken.org

@@ -1872,6 +1872,7 @@ So, the lowest location number in this example is *=35=*.
 
 #+begin_src scheme :exports none :noweb yes :tangle day5.scm
   (import (chicken fixnum)
+          (chicken sort)
           (chicken string)
           (chicken keyword)
           (chicken irregex))
@@ -2131,17 +2132,39 @@ function that handles the promises.
   <<day5-part1-map-entity-forward>>
   <<day5-part1-map-entity-forward-fully>>
   <<day5-part2-expand-seeds>>
+  <<day5-part2-fold-seeds>>
   <<day5-part2-calc>>
 #+end_src
 
 #+RESULTS: day5-part2-calc-full
-: 1181555926
+: 37806486
 
 #+begin_src scheme :noweb yes :exports none :tangle day5.scm
   (define (calc-part-2)
     <<day5-part2-calc>>)
 #+end_src
 
+*** The Optimized Solution
+
+For the optimized solution using ranges, a new record type is needed: ~ranged-entity~.
+
+#+begin_src scheme :tangle day5.scm
+  (define-record ranged-entity type from-id to-id)
+#+end_src
+
+To map the ~ranged-entity~ onto the next step, it has to be split up according to the
+~mapping-entry~ ranges.
+
+#+begin_src scheme :tangle day5.scm
+  (define (map-ranged-entity-forward ranged-entity mapping-alist)
+    (let* ((mapping-entries (alist-ref (ranged-entity-type ranged-entity) mapping-alist))
+           (mapping-entries-alist (map (lambda (x) (cons (mapping-entry-from-start x)
+                                                         x))
+                                       mapping-entries))
+           (sorted-range-starts (sort (map mapping-entry-from-start mapping-entries))))
+  ))
+#+end_src
+
 ** Puzzle Input
 
 #+NAME: day5-input