From 4bd4d1b4a17e938a84a5f0bc7810b402e1bb4ccd Mon Sep 17 00:00:00 2001
From: Rupus Reinefjord <rupus@reinefjord.net>
Date: Sun, 10 Dec 2023 22:32:02 +0100
Subject: [PATCH] day05

---
 2023/day05.nim | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 2023/day05.nim

diff --git a/2023/day05.nim b/2023/day05.nim
new file mode 100644
index 0000000..8a60be8
--- /dev/null
+++ b/2023/day05.nim
@@ -0,0 +1,70 @@
+import std/[sequtils, strutils, sugar, threadpool]
+
+type
+  CatMap = seq[tuple[srcStart, dstStart, range: int]]
+
+func get(catMap: CatMap, thing: int): int =
+  for m in catMap:
+    let
+      low = m.srcStart
+      high = m.srcStart + m.range - 1
+    if low <= thing and thing <= high:
+      return m.dstStart + (thing - m.srcStart)
+  return thing
+
+func location(catMaps: seq[CatMap], thing: int): int =
+  result = thing
+  for catMap in catMaps:
+    result = catMap.get(result)
+
+func catMaps(lines: seq[string]): CatMap =
+  for line in lines[1..^1]:
+    let
+      sp = line.split(' ')
+      ints = sp.map(parseInt)
+      md = (srcStart: ints[1], dstStart: ints[0], range: ints[2])
+    result.add(md)
+
+func parseSeeds(s: string): seq[int] = s.split(' ')[1..^1].map(parseInt)
+
+proc p1(input: string) =
+  let
+    parts = input.strip().split("\n\n")
+    seeds = parts[0].parseSeeds()
+    maps = parts[1..^1].mapIt(splitLines(it)).map(catMaps)
+  echo seeds.mapIt(location(maps, it)).min()
+
+func seedRanges(ranges: seq[int]): seq[(int, int)] =
+  for i in countup(0, ranges.high, 2):
+    let
+      start = ranges[i]
+      stop = start + ranges[i+1] - 1
+    result.add (start, stop)
+
+func lowest(maps: seq[CatMap], start, stop: int): int =
+  result = high(int)
+  for seed in start..stop:
+    let loc = maps.location(seed)
+    if loc < result:
+      result = loc
+  
+proc p2(input: string) =
+  let 
+    parts = input.strip().split("\n\n")
+    ranges = parts[0].parseSeeds()
+    maps = parts[1..^1].mapIt(splitLines(it)).map(catMaps)
+
+  let responses: seq[FlowVar[int]] = collect:
+    for (start, stop) in seedRanges(ranges):
+      spawn lowest(maps, start, stop)
+  sync()
+
+  let locations = collect:
+    for r in responses:
+      ^r
+  echo min(locations)
+
+when isMainModule:
+  let input = stdin.readAll()
+  p1(input)
+  p2(input)  # takes a minute or two.