# HG changeset patch
# User Steve Losh <steve@stevelosh.com>
# Date 1544407179 18000
# Node ID 8ffd80cd99aab89e85402dbd709bb064408613ba
# Parent  e24866ca76d61d8bd251581f45955a8bc7f4f4bb
Day 8

diff -r e24866ca76d6 -r 8ffd80cd99aa src/2018/main.lisp
--- a/src/2018/main.lisp	Fri Dec 07 20:58:35 2018 -0500
+++ b/src/2018/main.lisp	Sun Dec 09 20:59:39 2018 -0500
@@ -207,7 +207,7 @@
       (let ((graph (make-graph (mapcar #'parse-line data))))
         ;; (digraph.dot:draw graph)
         (recursively ((result nil))
-          (if (digraph:emptyp graph)
+          (if (emptyp graph)
             (coerce (nreverse result) 'string)
             (let ((next (extremum (digraph:leafs graph) 'char<)))
               (digraph:remove-vertex graph next)
@@ -230,5 +230,36 @@
           (when (null worker)
             (when-let ((task (pop available-tasks)))
               (setf worker (cons task (task-length task))))))
-        (when (and (digraph:emptyp graph) (every #'null workers))
+        (when (and (emptyp graph) (every #'null workers))
           (return elapsed))))))
+
+
+(define-problem (2018 8) (data)
+  (labels
+      ((make-node (children metadata) (cons metadata children))
+       (children (node) (cdr node))
+       (metadata (node) (car node))
+       (read-node (stream)
+         (let* ((children-count (read stream))
+                (metadata-count (read stream))
+                (children (iterate
+                            (repeat children-count)
+                            (collect (read-node stream) :result-type vector)))
+                (metadata (iterate
+                            (repeat metadata-count)
+                            (collect (read stream)))))
+           (make-node children metadata)))
+       (node-value (node &aux (children (children node)))
+         (if (emptyp children)
+           (summation (metadata node))
+           (iterate
+             (for meta :in (metadata node))
+             (for index = (1- meta))
+             (when (array-in-bounds-p children index)
+               (summing (node-value (aref children index))))))))
+    (let ((root (read-node data)))
+      (values
+        (recursively ((node root))
+          (+ (summation (metadata node))
+             (summation (children node) :key #'recur)))
+        (node-value root)))))
diff -r e24866ca76d6 -r 8ffd80cd99aa src/utils.lisp
--- a/src/utils.lisp	Fri Dec 07 20:58:35 2018 -0500
+++ b/src/utils.lisp	Sun Dec 09 20:59:39 2018 -0500
@@ -2,14 +2,18 @@
 
 ;;;; Problems -----------------------------------------------------------------
 (defmacro define-problem ((year day &optional part)
-                          (data-symbol reader)
+                          (data-symbol &optional reader)
                           &body body)
   (let ((function-name (if part
                          (symb 'advent- year '- day '/ part)
-                         (symb 'advent- year '- day))))
+                         (symb 'advent- year '- day)))
+        (path (format nil "data/~D/~2,'0D.txt" year day)))
     `(defun ,function-name ()
-       (let ((,data-symbol (,reader ,(format nil "data/~D/~2,'0D.txt" year day))))
-         ,@body))))
+       ,(if (null reader)
+          `(with-open-file (,data-symbol ,path)
+             ,@body)
+          `(let ((,data-symbol (,reader ,path)))
+             ,@body)))))
 
 
 ;;;; Readers ------------------------------------------------------------------
@@ -155,3 +159,22 @@
         (+ point #c(1 0))
         (+ point #c(0 -1))
         (+ point #c(-1 0))))
+
+
+(defgeneric emptyp (collection)
+  (:documentation "Return whether `collection` is empty."))
+
+(defmethod emptyp ((list list))
+  (null list))
+
+(defmethod emptyp ((vector vector))
+  (zerop (length vector)))
+
+(defmethod emptyp ((hash-table hash-table))
+  (zerop (hash-table-count hash-table)))
+
+(defmethod emptyp ((digraph digraph:digraph))
+  (digraph:emptyp digraph))
+
+(defmethod emptyp ((hset hash-set))
+  (hset-empty-p hset))