2023 Day 8 Part 1

2023/day08.nim

@@ -0,0 +1,58 @@
+import std/algorithm
+import std/enumerate
+import std/math
+import std/sequtils
+import std/sets
+import std/strscans
+import std/strutils
+import std/sugar
+import std/tables
+
+type Move {.pure.} = enum
+  L
+  R
+
+proc parseMove(c: char): Move =
+  case c:
+    of 'L': L
+    of 'R': R
+    else: raise newException(ValueError, $c)
+
+func parseMoves(line: string): seq[Move] =
+  line.map(parseMove)
+
+type Node = object
+  id: string
+  left: string
+  right: string
+
+proc parseNode(line: string): Node =
+  if not scanf(line, "$+ = ($+, $+)$.", result.id, result.left, result.right):
+    raise newException(ValueError, line)
+
+type Map = object
+  moves: seq[Move]
+  nodes: Table[string, Node]
+
+proc parseMap(text: string): Map =
+  let parts = text.strip.split("\n\n")
+  result.moves = parts[0].parseMoves
+  for node in parts[1].strip.splitLines.map(parseNode):
+    result.nodes[node.id] = node
+
+proc dbg[T](v: T): T = (echo(v); v)
+
+proc part1(): int =
+  let text = readFile("input/day08.txt")
+  var map = parseMap(text)
+
+  var mv = 0
+  var loc = "AAA"
+  while loc != "ZZZ":
+    case map.moves[mv mod len(map.moves)]:
+      of L: loc = map.nodes[loc].left
+      of R: loc = map.nodes[loc].right
+    mv = mv + 1
+  return mv
+
+echo part1()