this is a solution i'm not proud of

solutions/day03/example.txt

@@ -0,0 +1,10 @@
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..

solutions/day03/solution.nim

@@ -0,0 +1,88 @@
+import std/[strutils, sequtils, sets, tables]
+
+const example* = slurp("example.txt").strip()
+const input* = slurp("input.txt").strip()
+
+type
+  Pos = tuple[x, y: int]
+  # Symbol = tuple[c: char, pos: Pos]
+  Part = object
+    val: int
+    pos: Pos
+
+proc parseInput(input: string): seq[Part] =
+  var value: string
+  var parts: seq[Part]
+  for i, line in input.splitLines.toSeq():
+    for j, c in line:
+      if c in Digits:
+        value.add c
+        continue
+      if value.len > 0:
+        result.add Part(val: parseInt(value), pos: (x: j-value.len, y: i))
+        parts.add result[^1]
+        value = ""
+    if value.len > 0:
+      result.add Part(val: parseInt(value), pos: (x: line.len-1-value.len, y: i))
+      parts.add result[^1]
+      value = ""
+    parts = @[]
+
+proc dims(s: string): tuple[x: int, y: int] =
+  let lines = s.splitLines()
+  return (lines[0].len-1, lines.len-1)
+
+let nonSymbols = (Digits + {'.'}).toSeq().toHashSet()
+
+proc partNearSymbol(part: Part, input: string): bool =
+  let dimensions = input.dims
+  let
+    minY = max(part.pos.y - 1, 0)
+    minX = max(part.pos.x - 1, 0)
+    maxX = min(part.pos.x + ($part.val).len, dimensions.x)
+    maxY = min(part.pos.y + 1, dimensions.y)
+  var chars: seq[char]
+  for line in input.split("\n")[minY..maxY]:
+    chars &= line[minX..maxX].toSeq()
+  (chars.toHashSet() - nonSymbols).len > 0
+
+proc partOne*(input: string): int =
+  let parts = parseInput(input)
+  for part in parts:
+    if partNearSymbol(part, input):
+      result += part.val
+
+proc gearsNearPart(part: Part, input: string): seq[Pos] =
+  let dimensions = input.dims
+  let
+    minY = max(part.pos.y - 1, 0)
+    minX = max(part.pos.x - 1, 0)
+    maxX = min(part.pos.x + ($part.val).len, dimensions.x)
+    maxY = min(part.pos.y + 1, dimensions.y)
+  for i, line in input.split("\n")[minY..maxY]:
+    for j, c in line[minX..maxX]:
+      if c == '*':
+        result.add (x: minX+j, y: minY + i)
+
+proc partTwo*(input: string): int =
+  let parts = parseInput(input)
+  var gears: Table[Pos, seq[Part]]
+  for part in parts:
+    for gear in gearsNearPart(part, input):
+      if gear in gears: gears[gear].add part
+      else: gears[gear] = @[part]
+
+  for gear, parts in gears:
+    if parts.len == 2:
+      result += parts[0].val * parts[1].val
+
+when isMainModule:
+  import std/unittest
+
+  suite "day 3":
+    test "part one":
+      check partOne(example) == 4361
+      check partOne(input) == 536202
+    test "part two":
+      check partTwo(example) == 467835
+      check partTwo(input) == 78272573