From 496031e9c179e211d435fa18301670b0d96e5a76 Mon Sep 17 00:00:00 2001
From: Daniel Flanagan <daniel@lyte.dev>
Date: Fri, 11 Dec 2020 01:10:44 -0600
Subject: [PATCH] Day 11 part 1

---
 2020/src/day11.nim | 72 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 70 insertions(+), 2 deletions(-)

diff --git a/2020/src/day11.nim b/2020/src/day11.nim
index 7a4ee8f..7c7f0c7 100644
--- a/2020/src/day11.nim
+++ b/2020/src/day11.nim
@@ -1,7 +1,75 @@
-import streams
+import streams, sequtils, strutils
+
+type
+  Seat = enum Floor, Empty, Occupied
+  Grid = seq[seq[Seat]]
+
+doAssert @[@[Occupied, Empty], @[Floor, Empty]] == @[@[Occupied, Empty], @[Floor, Empty]]
+
+proc gridSummary(g: Grid): (int, int) =
+  ## Used during debugging
+  var o, v = 0
+  for y in 0..<g.len:
+    for x in 0..<g[y].len:
+      case g[y][x]:
+        of Empty: inc v
+        of Occupied: inc o
+        else: discard
+  (o, v)
+
+proc `$`(s: Seat): string =
+  case s
+    of Empty: "L"
+    of Occupied: "#"
+    else: "."
+
+proc gridLine(l: seq[Seat]): string = join(l.mapIt($it))
+
+proc toSeat(c: char): Seat =
+  case c
+    of 'L': Empty
+    of '#': Occupied
+    else: Floor
+
+proc asGrid(s: Stream): Grid =
+  for l in s.lines: result.add l.map toSeat
+
+proc getAdjacent(g: Grid, x: int, y: int): seq[Seat] =
+  for sy in y-1..y+1:
+    for sx in x-1..x+1:
+      if sy >= 0 and sx >= 0 and sy < g.len and sx < g[sy].len:
+        result.add g[sy][sx]
+
+proc stepGrid(g: Grid): Grid =
+  #echo "Step"
+  for y in 0..<g.len:
+    #echo g[y].gridLine
+    result.add @[]
+    for x in 0..<g[y].len:
+      let adj = getAdjacent(g, x, y)
+      result[y].add case g[y][x]
+        of Floor: Floor
+        of Empty:
+          if adj.countIt(it == Occupied) == 0:
+            Occupied
+          else:
+            Empty
+        of Occupied:
+          if adj.countIt(it == Occupied) >= 5:
+            Empty
+          else:
+            Occupied
+      #echo (x, y, g[y][x], gridSummary(@[adj]), adj.gridLine, result[y][x])
 
 proc part1*(s: Stream): int =
-  0
+  var g = s.asGrid
+  var ng: Grid
+  while g != ng:
+    echo "\n\nGrid:\n", g.gridSummary
+    ng = g
+    g = g.stepGrid
+  g.foldl(a.concat b).countIt(it == Occupied)
+
 
 proc part2*(s: Stream): int =
   0