day03.js

'use strict'  //  Binary Diagnostic

const { loadData } = require('./core/utils')
const rawInput = [loadData(module.filename)]

//  Compute domination for every column.
const computeDominants = (rows) => {
  const rowCount = rows.length, half = rowCount / 2, width = rows[0].length
  const mostOnes = new Array(width), mostZeros = new Array(width)

  for (let position = 0; position < width; position += 1) {
    let onesCount = 0

    for (let i = 0; i < rowCount; ++i) {
      if (rows[i][position] === '1') onesCount += 1
    }
    mostOnes[position] = onesCount > half ? '1' : '0'   //  '1' means 1 is dominating.
    mostZeros[position] = onesCount < half ? '1' : '0'  //  '1' means 0 is dominating.
  }

  return { mostOnes, mostZeros }
}

const puzzle1 = (rows) => {
  const { mostOnes, mostZeros } = computeDominants(rows)
  return Number.parseInt(mostOnes.join(''), 2) * Number.parseInt(mostZeros.join(''), 2)
}

const computeReadings = (rows, value1, value0) => {
  for (let pos = 0; rows.length > 1 && pos < rows[0].length; ++pos) {
    const { mostOnes, mostZeros } = computeDominants(rows), fits = []

    for (const word of rows) {
      const dominant = mostOnes[pos] === '1' ? value1
        : (mostZeros[pos] === '1' ? value0 : value1)

      if (word[pos] === dominant) fits.push(word)
    }
    rows = fits
  }
  return rows[0]
}

//  Advanced readings interpretation.
const puzzle2 = (rows) => {
  const oxy = computeReadings(rows, '1', '0')
  const co2 = computeReadings(rows, '0', '1')

  return Number.parseInt(oxy, 2) * Number.parseInt(co2, 2)
}

const parse = (dsn) => {
  let data = rawInput[dsn]

  if (data && (data = data.split('\n').filter(v => Boolean(v))).length) {
    return data
  }
}

rawInput[1] = `
00100
11110
10110
10111
10101
01111
00111
11100
10000
11001
00010
01010`

module.exports = { parse, puzzles: [puzzle1, puzzle2] }

/*
day03, set #1
	puzzle-1 (            126 µsecs): 198
	puzzle-2 (            295 µsecs): 230
day03, set #0
	puzzle-1 (            592 µsecs): 3309596
	puzzle-2 (           3401 µsecs): 2981085
 */