3 files changed, 48 insertions, 0 deletions
diff --git a/year2021/day7/maxima.mac b/year2021/day7/maxima.mac
new file mode 100644
index 0000000..a1c2d18
--- /dev/null
+++ b/year2021/day7/maxima.mac
@@ -0,0 +1,10 @@
+load("descriptive")$
+load("in.mac")$ /* Should define `input` list of numbers. */
+
+calcfuel(pos, distmod) :=
+    lreduce("+", map(lambda([n], distmod(abs(pos - n))), input))$
+
+calcfuel(median(input), lambda([x],x));
+calcfuel(floor(mean(input)), lambda([x], (x*(x+1)/2)));
+calcfuel(floor(mean(input)) + 1, lambda([x], (x*(x+1)/2)));
+
diff --git a/year2021/day7/part1.clj b/year2021/day7/part1.clj
new file mode 100644
index 0000000..f08e5b4
--- /dev/null
+++ b/year2021/day7/part1.clj
@@ -0,0 +1,18 @@
+(defn median [lst]
+  (as-> (count lst) $
+    (quot $ 2)
+    (subvec (vec (sort lst)) (dec $) (inc $))
+    (if (even? (count lst)) (apply + $) (second $))
+    (quot $ 2)
+    )
+  )
+
+(as-> (slurp "./in") $ ; "16,1,2,0,4,2,7,1,2,14"
+      (clojure.string/split $ #",")
+      (mapv read-string $)
+      (map (partial - (median $)) $)
+      (map #(Math/abs %) $)
+      (apply + $)
+      (println $)
+      )
+
diff --git a/year2021/day7/part2.clj b/year2021/day7/part2.clj
new file mode 100644
index 0000000..b96b55d
--- /dev/null
+++ b/year2021/day7/part2.clj
@@ -0,0 +1,20 @@
+(defn calc-fuel [lst pos]
+  (reduce #(as-> %2 $
+             (- pos $)
+             (Math/abs $)
+             (/ (* $ (inc $)) 2)
+             (+ %1 $)
+             )
+          0 lst
+          )
+  )
+
+(let [input (as-> (slurp "./in") $ ;"16,1,2,0,4,2,7,1,2,14"
+                  (clojure.string/split $ #",")
+                  (map read-string $)
+                  )
+      mean (quot (apply + input) (count input))]
+  (println (min (calc-fuel input mean)
+                (calc-fuel input (inc mean))))
+  )
+