1 files changed, 83 insertions, 0 deletions

diff --git a/day18/solution.nim b/day18/solution.nim
new file mode 100644
index 0000000..0ef81fb
--- /dev/null
+++ b/day18/solution.nim
@@ -0,0 +1,83 @@
+import strutils
+import sequtils
+import sugar
+import sets
+
+type Cube = tuple
+  x, y, z: int
+
+proc parseLine(line: string): Cube =
+  let tokens = map(line.split(","), (e) => e.parseInt())
+  (tokens[0], tokens[1], tokens[2])
+
+proc parseFile(content: string): seq[Cube] =
+  let lines = content.strip().splitLines()
+  result = map(lines, parseLine)
+
+proc nextTo(A, B: Cube): bool =
+  let
+    dx = abs(A.x - B.x)
+    dy = abs(A.y - B.y)
+    dz = abs(A.z - B.z)
+
+  dx + dy + dz <= 1 and dx <= 1 and dy <= 1 and dz <= 1
+
+proc part1(cubes: seq[Cube]): int =
+  result = 6 * cubes.len()
+  for i, cube in cubes[0 .. ^2]:
+    for other in cubes[i+1 .. ^1]:
+      if cube.nextTo(other):
+        result -= 2
+
+var
+  solid: HashSet[Cube]
+  visited: HashSet[Cube]
+  maxn = 0
+  minn = -1
+
+proc blocksAround(cube: Cube): int =
+  for x in [cube.x-1, cube.x+1]:
+    if (x, cube.y, cube.z) in solid:
+      result += 1
+
+  for y in [cube.y-1, cube.y+1]:
+    if (cube.x, y, cube.z) in solid:
+      result += 1
+
+  for z in [cube.z-1, cube.z+1]:
+    if (cube.x, cube.y, z) in solid:
+      result += 1
+
+proc dfs(curr: Cube): int =
+  let maxp = max([curr.x, curr.y, curr.z])
+  let minp = min([curr.x, curr.y, curr.z])
+  if minp < minn or maxp >= maxn or visited.containsOrIncl(curr):
+    return 0
+
+  # if is air block
+  if curr notin solid:
+    result = blocksAround(curr) +
+      dfs((curr.x+1, curr.y, curr.z)) +
+      dfs((curr.x-1, curr.y, curr.z)) +
+      dfs((curr.x, curr.y+1, curr.z)) +
+      dfs((curr.x, curr.y-1, curr.z)) +
+      dfs((curr.x, curr.y, curr.z+1)) +
+      dfs((curr.x, curr.y, curr.z-1))
+
+
+proc part2(cubes: seq[Cube]): int =
+  # echo cubes
+  for cube in cubes:
+    maxn = max([cube.x, cube.y, cube.z])
+  maxn += 6
+
+  for cube in cubes:
+    solid.incl(cube)
+
+  result = dfs((0,0,0))
+
+let content = readFile("./input.txt")
+let input = parseFile(content)
+
+echo part1(input)
+echo part2(input)