advent-of-code/2020/src/day14.nim
2020-12-14 13:01:58 -06:00

47 lines
1.1 KiB
Nim

import streams, strutils, bitops, tables
proc asMasks(s: string): (uint64, uint64) =
var ones, zeroes = 0'u64
for c in s:
ones = rotateLeftBits(ones, 1'u8)
zeroes = rotateLeftBits(zeroes, 1'u8)
case c:
of '1': ones.setBit(0'u8)
of '0': zeroes.setBit(0'u8)
else: discard
echo ("Masks:", ones, zeroes)
return (ones, zeroes)
doAssert "01X".asMasks() == (2'u64, 4'u64)
proc withMasks(n: uint64, mask: (uint64, uint64)): uint64 =
echo n.toBin
n.bitand(mask[1]).bitnot.bitand(mask[0].bitnot).bitnot
proc part1*(s: Stream): int =
var masks: (uint64, uint64)
var memory = newTable[uint64, uint64]()
var i = 0
for l in s.lines:
if l.startsWith("mask = "):
masks = l.split(" = ")[1].asMasks
elif l.startsWith("mem["):
let ll = l.split("[")[1].split("] = ")
memory[ll[0].parseUInt] = ll[1].parseUInt.withMasks(masks)
inc i
echo memory
for v in memory.values: result += int v
# 9,639,694,085,526 is too high
let n = """
mask = XXXXXXXXXXXXXXXXXXXXXXXXXXXXX1XXXX0X
mem[8] = 11
mem[7] = 101
mem[8] = 0
""".newStringStream.part1()
echo n
doAssert n == 165
proc part2*(s: Stream): int =9