Add day6 problem + solution

day6/p2.nim

@@ -0,0 +1,55 @@
+import os, sequtils, tables
+import std/strutils
+
+const SIM_DAYS = 256
+
+proc main() =
+  let fileName = paramStr(1)
+
+  let f = fileName.open(fmRead)
+
+  let lanternFishSim = {
+    0: 0,
+    1: 0,
+    2: 0,
+    3: 0,
+    4: 0,
+    5: 0,
+    6: 0,
+    7: 0,
+    8: 0
+  }.newTable
+
+  for num in f.readLine().split(",").mapIt(it.parseInt):
+    lanternFishSim[num] += 1
+
+  f.close()
+
+  for i in 0 ..< SIM_DAYS:
+
+    let
+      temp0 = lanternFishSim[0]
+      temp1 = lanternFishSim[1]
+      temp2 = lanternFishSim[2]
+      temp3 = lanternFishSim[3]
+      temp4 = lanternFishSim[4]
+      temp5 = lanternFishSim[5]
+      temp6 = lanternFishSim[6]
+      temp7 = lanternFishSim[7]
+      temp8 = lanternFishSim[8]
+
+    # move the fish down and add 7 and 0 together
+    # to simulate reproduction
+    lanternFishSim[8] = temp0
+    lanternFishSim[7] = temp8
+    lanternFishSim[6] = temp7 + temp0
+    lanternFishSim[5] = temp6
+    lanternFishSim[4] = temp5
+    lanternFishSim[3] = temp4
+    lanternFishSim[2] = temp3
+    lanternFishSim[1] = temp2
+    lanternFishSim[0] = temp1
+
+  echo "NumFish: ", toSeq(lanternFishSim.values()).foldl(a + b)
+
+main()