Advent of Code 2021 - Day 3
inputFile = FileAttachment("input.txt").text()
nums = inputFile.split('\n')
Part 1
gamma = {
let numDigits = nums[0].length
let counts = ({zeros: [], ones: []})
for (let pos = 0; pos < numDigits; pos++) {
// this kind of transposes the 'matrix' of numbers so we can we have arrays of first digits, second digits, etc.
counts.zeros[pos] = nums.map((x) => x[pos]).filter((x) => x === '0').length
counts.ones[pos] = nums.map((x) => x[pos]).filter((x) => x === '1').length
}
let gamma = []
for (let pos = 0; pos < numDigits; pos++) {
if (counts.zeros[pos] > counts.ones[pos]) {
gamma[pos] = '0'
} else {
gamma[pos] = '1'
}
}
return gamma.join('')
}
epsilon = {
let numDigits = nums[0].length
let epsilon = []
for (let pos = 0; pos < numDigits; pos++) {
if (gamma[pos] === '1') {
epsilon[pos] = '0'
} else {
epsilon[pos] = '1'
}
}
return epsilon.join('')
}
power = {
let gammaRate = parseInt(gamma, 2)
let epsilonRate = parseInt(epsilon, 2)
return gammaRate * epsilonRate
}
Part 2
oxRating = {
let numDigits = nums[0].length
let keep = nums
for (let pos = 0; pos < numDigits; pos++) {
let zeroCount = keep.map(x => x[pos]).filter(x => x === '0').length
let oneCount = keep.map(x => x[pos]).filter(x => x === '1').length
if (zeroCount > oneCount) {
keep = keep.filter(x => x[pos] === '0')
} else {
keep = keep.filter(x => x[pos] === '1')
}
if (keep.length === 1) {
return parseInt(keep.join(), 2)
}
}
return parseInt(keep.join(), 2)
}
co2Rating = {
let numDigits = nums[0].length
let keep = nums
for (let pos = 0; pos < numDigits; pos++) {
let zeroCount = keep.map(x => x[pos]).filter(x => x === '0').length
let oneCount = keep.map(x => x[pos]).filter(x => x === '1').length
if (zeroCount > oneCount) {
keep = keep.filter(x => x[pos] === '1')
} else {
keep = keep.filter(x => x[pos] === '0')
}
if (keep.length === 1) {
return parseInt(keep.join(), 2)
}
}
return parseInt(keep.join(), 2)
}
oxRating * co2Rating
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