2023 Day 6 Part 1

2023/day06.nim

@@ -0,0 +1,60 @@
+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 Race = tuple
+  time: int
+  distance: int
+
+func parseRaces(text: string): seq[Race] =
+  let lines = text.strip.splitLines
+  let times = lines[0].splitWhitespace
+  let distances = lines[1].splitWhitespace
+  assert(times[0] == "Time:")
+  assert(distances[0] == "Distance:")
+
+  for (time, distance) in zip(times[1..^1], distances[1..^1]):
+    result.add (time.parseInt, distance.parseInt)
+
+func distance_traveled(race: Race, hold_ms: int): int =
+  let travel_time = max(0, race.time - hold_ms)
+  let speed = hold_ms
+  speed * travel_time
+
+func min_win(race: Race): int =
+  var hold_ms = 0
+  while hold_ms < race.time:
+    let dist = race.distance_traveled(hold_ms)
+    if dist > race.distance:
+      return hold_ms
+    inc hold_ms
+
+func max_win(race: Race): int =
+  var hold_ms = race.time - 1
+  while hold_ms > 0:
+    let dist = race.distance_traveled(hold_ms)
+    if dist > race.distance:
+      return hold_ms
+    dec hold_ms
+
+func win_count(race: Race): int =
+  let min_ms = race.min_win
+  let max_ms = race.max_win
+  len(min_ms .. max_ms)
+
+proc dbg[T](v: T): T = (echo(v); v)
+
+proc part1(): int =
+  let text = readFile("input/day06.txt")
+  let races = parseRaces(text)
+
+  result = 1
+  for race in races:
+    result *= dbg(race.win_count)
+
+echo part1()