day 7: nim

1 files changed, 35 insertions, 0 deletions

diff --git a/d7.nim b/d7.nim
new file mode 100644
index 0000000..536897d
--- /dev/null
+++ b/d7.nim
@@ -0,0 +1,35 @@
+import std/algorithm, std/os, std/sugar, std/strutils, std/math
+
+proc read_crabs(filename: string): seq[int] =
+   let f = open(filename)
+   defer: f.close()
+   result = collect:
+      for crab in f.read_all().split(','):
+         parse_int(crab.strip())
+
+func part1(crabs: seq[int]): int =
+   let median = sorted(crabs)[len(crabs) div 2]
+   for crab in crabs:
+      result += abs(crab - median)
+
+func part2_fuel(crabs: seq[int], pos: int): int =
+   for crab in crabs:
+      let dist = abs(crab - pos)
+      result += dist * (dist + 1) div 2
+
+func part2(crabs: seq[int]): int =
+   let
+      l = len(crabs)
+      s = sum(crabs)
+   var c = 0
+   for crab in crabs:
+      if crab * l > s: inc c
+   return part2_fuel(crabs, (s + c) div l)
+
+when is_main_module:
+   var filename: string = "7.in"
+   if param_count() == 1:
+      filename = param_str(1)
+   let crabs = read_crabs(filename)
+   echo part1(crabs)
+   echo part2(crabs)