Day 19: Solve part 1 and 2

Author: nihas101

Diff for: src/advent_of_code_2023/day19.clj

@@ -2,8 +2,114 @@
   (:require
    [advent-of-code-2023.utils.string :as u]))
 
-(defn parse-input [input])
+(defn- parse-condition [condition]
+  (let [[p fun comp] (re-seq #"\d+|[^<>=]+|[<>=]" condition)]
+    [(cond
+       fun (let [fun (resolve (read-string fun))
+                 y (Long/parseLong comp)]
+             (fn [part] (fun (part p) y)))
+       (= p "A") (constantly "A")
+       (= p "R") (constantly "R")
+       :else (constantly p))
+     fun p (if fun (Long/parseLong comp) comp)]))
 
-(defn day19-1 [parsed-input])
+(defn- parse-rule [rule]
+  (let [[condition target] (u/split-sections rule #":")
+        [cond-fun fun p comp] (parse-condition condition)]
+    {:condition cond-fun
+     :fun fun
+     :p p
+     :comp comp
+     :target target}))
 
-(defn day19-2 [parsed-input])
+(defn- parse-rules [rules]
+  (when rules
+    (mapv parse-rule (u/split-sections rules #","))))
+
+(defn- parse-parts [parts]
+  (when parts
+    (mapv (fn [part-ratings]
+            (transduce
+             (map (fn [[k v]] [k (Long/parseLong v)]))
+             conj {} (partition-all 2 (re-seq #"[a-z]+|\d+" part-ratings))))
+          (u/split-sections parts u/line-endings))))
+
+(defn- parse-line [line]
+  (let [[workflow rules]
+        (u/split-sections line #"\{|\}")]
+    {workflow (parse-rules rules)}))
+
+(defn parse-input [input]
+  (when input
+    (let [[wf-input parts] (u/split-sections input)]
+      {:workflows (transduce
+                   (map parse-line)
+                   merge (u/split-sections wf-input u/line-endings))
+       :part-ratings (parse-parts parts)})))
+
+(defn- run-workflow [workflow part-rating]
+  (loop [[{:keys [condition target]} & wf] workflow]
+    (let [result (condition part-rating)]
+      (cond
+        (string? result) result
+        result target
+        :else (recur wf)))))
+
+(defn- workflow [workflows]
+  (fn [part-rating workflow]
+    (let [next-workflow (run-workflow (workflows workflow) part-rating)]
+      (cond
+        (#{"R" "A"} next-workflow) (= "A" next-workflow)
+        (string? next-workflow) (recur part-rating next-workflow)
+        (keyword? next-workflow) next-workflow))))
+
+(defn day19-1 [{:keys [workflows part-ratings]}]
+  (transduce
+   (comp
+    (filter #((workflow workflows) % "in"))
+    (map (juxt #(get % "x") #(get % "m") #(get % "a") #(get % "s")))
+    (map (partial reduce +)))
+   + part-ratings))
+
+(defn- shorten-range-left [[^long a ^long b] ^long c]
+  [(max a c) b])
+
+(defn- shorten-range-right [[^long a ^long b] ^long c]
+  [a (min b c)])
+
+(defn- split-range [part-rating-ranges fun p ^long comp]
+  (condp = fun
+    "<" [(update part-rating-ranges p shorten-range-left comp)
+         (update part-rating-ranges p shorten-range-right (dec comp))]
+    ">" [(update part-rating-ranges p shorten-range-right comp)
+         (update part-rating-ranges p shorten-range-left (inc comp))]))
+
+(defn combinations-count [ranges]
+  (transduce
+   (map (fn [[^long mi ^long ma]] (- (inc ma) mi)))
+   * (vals ranges)))
+
+(defn- valid-input-ranges [wf-name
+                           [{:keys [fun p comp target]} & wfs]
+                           workflows
+                           part-rating-ranges]
+  (cond
+    (= wf-name "A") [part-rating-ranges]
+    (= wf-name "R") []
+    fun (let [[wf-false wf-true] (split-range part-rating-ranges fun p comp)]
+          (into (valid-input-ranges wf-name wfs
+                                    workflows wf-false)
+                (valid-input-ranges target (workflows target)
+                                    workflows wf-true)))
+    p (recur p (workflows p) workflows part-rating-ranges)))
+
+(defn day19-2 [{:keys [workflows]}]
+  (transduce
+   (map combinations-count)
+   + (valid-input-ranges "in"
+                         (workflows "in")
+                         workflows
+                         {"x" [1 4000]
+                          "m" [1 4000]
+                          "a" [1 4000]
+                          "s" [1 4000]})))

Diff for: src/advent_of_code_2023/utils/graph.clj

@@ -22,7 +22,7 @@
          visited visited
          path-val (path-fn)]
     (let [[c] (first q)
-          q (if (seq q) (pop q) nil)]
+          q (when (seq q) (pop q))]
       (cond
         (continue? c) (let [nz (neighbours c visited)]
                         (recur (reduce assoc-to-priority-map q nz)

Diff for: test/advent_of_code_2023/day19_test.clj

@@ -4,26 +4,38 @@
    [advent-of-code-2023.day19 :refer :all]
    [advent-of-code-2023.test-utils :as tu]))
 
-(defonce ^:private example-input (parse-input ""))
+(defonce ^:private example-input (parse-input "px{a<2006:qkq,m>2090:A,rfg}
+pv{a>1716:R,A}
+lnx{m>1548:A,A}
+rfg{s<537:gd,x>2440:R,A}
+qs{s>3448:A,lnx}
+qkq{x<1416:A,crn}
+crn{x>2662:A,R}
+in{s<1351:px,qqz}
+qqz{s>2770:qs,m<1801:hdj,R}
+gd{a>3333:R,R}
+hdj{m>838:A,pv}
+
+{x=787,m=2655,a=1222,s=2876}
+{x=1679,m=44,a=2067,s=496}
+{x=2036,m=264,a=79,s=2244}
+{x=2461,m=1339,a=466,s=291}
+{x=2127,m=1623,a=2188,s=1013}"))
 
 (def ^:private input (parse-input (tu/slurp-input "resources/day19.txt")))
 
 (deftest day19-1-example-test
   (testing "day19-1 example"
-    (is (= nil
-           (day19-1 example-input)))))
+    (is (= 19114 (day19-1 example-input)))))
 
 (deftest day19-1-test
   (testing "day19-1"
-    (is (= nil
-           (day19-1 input)))))
+    (is (= 397134 (day19-1 input)))))
 
 (deftest day19-2-example-test
   (testing "day19-2 example"
-    (is (= nil
-           (day19-2 example-input)))))
+    (is (= 167409079868000 (day19-2 example-input)))))
 
 (deftest day19-2-test
   (testing "day19-2"
-    (is (= nil
-           (day19-2 input)))))
+    (is (= 127517902575337 (day19-2 input)))))