advent-of-code/2021/nim/day3.nim
2021-12-13 14:47:22 -06:00

79 lines
2.7 KiB
Nim

import std/[strutils, sequtils, options, math, parseutils]
import ./common
const ASCII_ZERO = int('0')
type BitCounter = object
zeroes: int
ones: int
proc countBits(inputs: seq[string], maybeWidth: Option[int], offset = 0): seq[BitCounter] =
let width = maybeWidth.get(inputs[0].len())
let maxIndex = offset+width
for i in offset..<maxIndex: result.add(BitCounter(zeroes: 0, ones: 0))
for binstring in inputs:
for i in offset..<maxIndex:
let outIndex = i - offset
if (binstring[i].int() - ASCII_ZERO) > 0: inc result[outIndex].ones
else: inc result[outIndex].zeroes
proc powerConsumption(inputs: seq[string]): int =
let counters = inputs.countBits(none(int))
let width: Natural = inputs[0].len()
for i in 0..<width:
if counters[i].ones > counters[i].zeroes: inc result
result = result shl 1
result = result shr 1
result = result * (result xor ((2 ^ width) - 1))
proc lifeSupportRating(inputs: seq[string]): int =
let width: Natural = inputs[0].len()
var oxygenRating, co2Rating = 0
var oxygenCandidates, co2Candidates: seq[int] = toSeq(0..<inputs.len)
for i in 0..<width:
var newOxygenCandidates, newCo2Candidates: seq[int] = @[]
if oxygenRating == 0:
let candidates = oxygenCandidates.mapIt(inputs[it])
let counters = countBits(candidates, some(1), i)
let moreCommon: char = if counters[0].ones >= counters[0].zeroes: '1' else: '0'
for j in oxygenCandidates:
if inputs[j][i] == moreCommon:
newOxygenCandidates.add(j)
if newOxygenCandidates.len() == 1:
discard inputs[newOxygenCandidates[0]].parseBin(oxygenRating)
if co2Rating == 0:
let candidates = co2Candidates.mapIt(inputs[it])
let counters = countBits(candidates, some(1), i)
let lessCommon: char = if counters[0].zeroes <= counters[0].ones: '0' else: '1'
for j in co2Candidates:
if inputs[j][i] == lessCommon:
newCo2Candidates.add(j)
if newCo2Candidates.len() == 1:
discard inputs[newCo2Candidates[0]].parseBin(co2Rating)
oxygenCandidates = newOxygenCandidates
co2Candidates = newCo2Candidates
if oxygenRating != 0 and co2Rating != 0: break
return oxygenRating * co2Rating
let input = 3.loadInput()
time("powerConsumption part 1"): echo input.powerConsumption()
time("lifeSupportRating part 2"): echo input.lifeSupportRating()
when not defined(release):
static:
let testInput = @[
"00100",
"11110",
"10110",
"10111",
"10101",
"01111",
"00111",
"11100",
"10000",
"11001",
"00010",
"01010",
]
doAssert testInput.powerConsumption() == 198
doAssert testInput.lifeSupportRating() == 230