1 files changed, 83 insertions, 0 deletions
diff --git a/year2021/day5/part2.clj b/year2021/day5/part2.clj
new file mode 100644
index 0000000..d324618
--- /dev/null
+++ b/year2021/day5/part2.clj
@@ -0,0 +1,83 @@
+(require '[clojure.string :as str])
+
+(defn read-coords []
+  (let [line (read-line)]
+    (when (not (empty? line))
+      (mapv
+        #(Integer/parseInt %)
+        (str/split
+          line
+          #"[^\d]+"
+          )
+        )
+      )
+    )
+  )
+
+(defn read-all-coords []
+  (loop [cds [] c (read-coords)]
+    (if (empty? c)
+      cds
+      (recur
+        (conj cds c)
+        (read-coords)
+        )
+      )
+    )
+  )
+
+(defn mark-coord [cmap x y]
+  (update
+    cmap
+    [x y]
+    #(if (nil? %) 0 (inc %))
+    )
+  )
+
+(defn mark-coords [cmap x1 y1 x2 y2]
+  (cond
+    (= y1 y2)
+    (reduce
+      #(mark-coord %1 %2 y1)
+      cmap
+      (range (min x1 x2) (inc (max x1 x2)))
+      )
+    (= x1 x2)
+    (reduce
+      #(mark-coord %1 x1 %2)
+      cmap
+      (range (min y1 y2) (inc (max y1 y2)))
+      )
+    :else
+    (let [ic (if (< x1 x2) [x1 y1] [x2 y2])
+          ec (if (> x1 x2) [x1 y1] [x2 y2])
+          dy (if (> (second ec) (second ic)) 1 -1)
+          ]
+      (loop [cm cmap c ic]
+        (if (> (first c) (first ec))
+          cm
+          (recur
+            (apply (partial mark-coord cm) c)
+            [(inc (first c)) (+ dy (second c))]
+            )
+          )
+        )
+      )
+    )
+  )
+
+(def finished-map
+  (reduce
+    #(apply (partial mark-coords %1) %2)
+    {}
+    (read-all-coords)
+    )
+  )
+
+(->> finished-map
+     (vals)
+     (filter pos?)
+     (count)
+     (println)
+     )
+