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import std/os, std/sugar, std/strutils, std/sequtils
type
OctoState = Natural
Map = tuple[map: seq[OctoState], width: int, height: int]
proc read_map(filename: string): Map =
let f = open(filename)
defer: f.close()
result.map = collect:
for line in f.lines():
result.width = line.len
result.height += 1
for c in line:
(c.ord - '0'.ord).OctoState
proc print_map(map: Map) =
for y in countup(0, map.height - 1):
for x in countup(0, map.width - 1):
stdout.write(('0'.ord + map.map[x + map.width * y]).char)
stdout.write('\n')
proc solve(map: Map): tuple[part1, part2: int] =
var
current = map.map
flashed = new_seq[bool](current.len)
flash = new_seq[bool](current.len)
flashes = 0
for step in 1..1000:
#print_map((current, map.width, map.height))
#echo ""
flashed.apply(proc(_: bool): bool = false)
current.apply(proc(s: OctoState): OctoState = s + 1)
while true:
var any = false
flash.apply(proc(_: bool): bool = false)
for i, s in current:
if flashed[i] or s <= 9: continue
flashed[i] = true
flash[i] = true
any = true
if not any: break
for i, s in flash:
if not s: continue
let
x = i mod map.width
y = i div map.width
for dy in countup(-1, 1):
for dx in countup(-1, 1):
if dx == 0 and dy == 0: continue
let
x = x + dx
y = y + dy
if x < 0 or x >= map.width: continue
if y < 0 or y >= map.height: continue
inc current[x + map.width * y]
var sum = 0
for i, s in flashed:
if not s: continue
current[i] = 0
inc sum
flashes += sum
if step == 100:
result.part1 = flashes
if sum == map.width * map.height:
result.part2 = step
break
when is_main_module:
var filename: string = "11.in"
if param_count() == 1:
filename = param_str(1)
let map = read_map(filename)
let (part1, part2) = solve(map)
echo part1
echo part2
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