graveyard/aoc2020/p15.nim
2022-05-09 11:58:15 -05:00

33 lines
592 B
Nim

import tables
iterator play(start: seq[int]): int =
var spoke = initTable[int, int]()
var turn = 0
var nextSpeak = 0
for i in start:
turn += 1
spoke[i] = turn
yield i
nextSpeak = 0
while true:
turn += 1
yield nextSpeak
var lastSpoke = spoke.getOrDefault(nextSpeak, -1)
spoke[nextSpeak] = turn
if lastSpoke == -1:
nextSpeak = 0
else:
nextSpeak = turn - lastSpoke
proc solve(s: seq[int], n: int): int =
var i = 0
for x in play(s):
inc i
if i == n:
echo x
break
echo solve(@[5,1,9,18,13,8,0], 30000000)