Advent-of-Code-2018.js

/******** ANSWERS ********/

// ⭐: 1
const addThemAllUp = frequencyChanges => frequencyChanges.reduce((a, b) => a + b)

// ⭐: 2
const findFirstRepeatedFrequency = frequencyChanges => {
  let index = 0
  let currentFrequency = 0
  const frequencies = new Set()
  while (true) {
    frequencies.add(currentFrequency)
    currentFrequency += frequencyChanges[index]

    if (frequencies.has(currentFrequency)) {
      break
    } else {
      index = index === frequencyChanges.length - 1 ? 0 : index + 1
    }
  }
  return currentFrequency
}

// ⭐: 3
const getBoxIdChecksum = boxIds => {
  const counts = {2: 0, 3: 0}
  for (const boxId of boxIds) {
    if (anyCharAppearsNTimes(boxId, 2)) counts[2]++
    if (anyCharAppearsNTimes(boxId, 3)) counts[3]++
  }
  return counts[2] * counts[3]	
}

// ⭐: 4
const findPrototypeFabric = boxIds => {
  boxIds = [...boxIds]
  let currentBoxId

  while (boxIds.length > 0) {
    currentBoxId = boxIds.pop()
    
    for (const boxId of boxIds) {
      let differenceCount = 0
      let differingIndex

      for (const index in currentBoxId) {
        if (currentBoxId[index] !== boxId[index]) {
          differenceCount++
          differingIndex = parseInt(index)
        }
        if (differenceCount > 1) break
      }

      if (differenceCount === 1) {
        return replaceCharAt(differingIndex, currentBoxId, '')
      }
    }
  }
}

// ⭐: 4 (With ES6 destructuring and recursion)
const findPrototypeFabricR = ([currentBoxId, ...otherBoxIds]) => {
  if (!currentBoxId) return null
  return prototypeFabricFound(currentBoxId, otherBoxIds) || findPrototypeFabricR(otherBoxIds)
}


// ⭐: 5
const countOverlappingClaims = claims => {
  const matrix = addAllClaimsToMatrix(claims)
  const overlappingCoords = Object.values(matrix).filter(coord => coord.length > 1)
  return overlappingCoords.length
}

// ⭐: 6
const findFirstNonOverlappingClaim = claims => {
	const matrix = addAllClaimsToMatrix(claims)
	for (const claim of claims) {
		if (claimDoesntOverlap(claim, matrix)) return claim
	}
}

/******** HELPERS ********/

// get day 1 data ready to operate on
const getDay1Data = () =>
  fetch('https://adventofcode.com/2018/day/1/input')
    .then(resp => resp.text())
    .then(text => text.split('\n').slice(0, -1))
    .then(arr => arr.map(n => parseInt(n)))

// get day 2 data ready to operate on
const getDay2Data = () =>
  fetch('https://adventofcode.com/2018/day/2/input')
    .then(resp => resp.text())
    .then(text => text.split('\n').slice(0, -1))

// get day 3 data ready to operate on
const getDay3Data = () =>
  fetch('https://adventofcode.com/2018/day/3/input')
    .then(resp => resp.text())
    .then(text => text.split('\n').slice(0, -1))
    .then(data => data.map(parseClaim)

// check if any char in a string appears a given number of times
const anyCharAppearsNTimes = (string, times) => {
  const charSet = new Set(string)
  for (const char of charSet) {
    const match = string.match(new RegExp(char, 'g'))
    if (match && match.length === times) return true
  }
  return false
}

// return a copy of a string with a char replaced at a given index
const replaceCharAt = (index, string, replacement) =>
  string.slice(0, index) + replacement + string.slice(index + 1)

// check if prototype fabric is found in a single loop
const prototypeFabricFound = (currentBoxId, boxIds) => {
  for (const boxId of boxIds) {
    let differenceCount = 0
    let differingIndex

    for (const index in currentBoxId) {
      if (currentBoxId[index] !== boxId[index]) {
        differenceCount++
        differingIndex = parseInt(index)
      }
      if (differenceCount > 1) break
    }

    if (differenceCount === 1) {
      return replaceCharAt(differingIndex, currentBoxId, '')
    }
  }
}

// convert a claim string into a claim object
const parseClaim = claim => {
  const match = claim.match(/#(\d+)\s@\s(\d+),(\d+):\s(\d+)x(\d+)/)
  return {
    id: parseInt(match[1]),
    x: parseInt(match[2]),
    y: parseInt(match[3]),
    w: parseInt(match[4]),
    h: parseInt(match[5])
  }
}

// add all coords for a single claim into an object "matrix"
const addClaimToMatrix = (claim, matrix) => {
  for (let i = 0; i < claim.w; i++) {
    const x = claim.x + 1 + i

    for (let i = 0; i < claim.h; i++) {
      const y = claim.y + 1 + i
      const tile = `${x},${y}`
      matrix[tile] = matrix[tile] ? [...matrix[tile], claim.id] : [claim.id]
    }
  }
  return matrix
}

// take a list of claims and add them all to a new object
const addAllClaimsToMatrix = claims =>
  claims.reduce((matrix, claim) => addClaimToMatrix(claim, matrix), {})

// check if a single claim overlaps
const claimDoesntOverlap = (claim, matrix) =>
  Object.values(matrix)
    .filter(tile => tile.includes(claim.id))
    .every(tile => tile.length === 1)

@MinimumViablePerson - Super cool. I actually didn't know that feature about Sets. I knew they forced uniqueness, but didn't realize it was because they didn't need values. Looking at MDN, they can have values though, right?

@stephencweiss Yeah, they only have values in a sense. There's no key/value pair to them, and they are unique. They can have a much faster add and look up performance.