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Merge pull request #204 from amclin/feat/2021-day-06
Feat/2021 day 06
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‎2021/day-06/fish.js

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let _fishes = []
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const NewFishAge = 8 // age of newly spawned fish
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const FishSpawnAge = 0 // age when the fish spawns
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const ResetFishAge = 6 // age of the original fish after spawning
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// allocate an empty big school
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const _newBigSchool = () => [...new Array(NewFishAge + 1)].map(() => 0)
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let _bigSchool = _newBigSchool()
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const ageFish = (age) => {
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if (age > NewFishAge) { throw new Error('Fish is too young') }
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if (age < FishSpawnAge) { throw new Error('Fish is too old') }
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if (age === FishSpawnAge) { return ResetFishAge }
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return age - 1
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}
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const spawn = (qty) => {
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console.debug(`spawning ${qty} fish`)
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const newFishes = [...new Array(qty)].map(() => NewFishAge)
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_fishes.push(...newFishes)
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}
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const efficientSpawn = (qty) => {
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console.debug(`spawning ${qty} fish`)
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_bigSchool[NewFishAge] = qty
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}
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const school = {
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get state () {
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return _fishes
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},
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set state (state) {
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_fishes = state
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},
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advance: () => {
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// Calculate how many will spawn
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const toSpawn = _fishes.filter((x) => x === FishSpawnAge).length
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// Iterate each fish
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_fishes = _fishes.map(ageFish)
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// Spawn the new fish
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spawn(toSpawn)
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}
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}
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/**
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* The efficient school doesn't track the position of the fish.
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* It only cares about the total number of fish of each age
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*/
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const efficientSchool = {
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get state () {
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return _bigSchool
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},
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set state (state) {
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_bigSchool = _newBigSchool()
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state.forEach((fish) => { _bigSchool[fish]++ })
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},
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advance: () => {
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// Calculate how many will spawn (age 0) and shift the age groups in one quick step
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const toSpawn = _bigSchool.shift()
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// Iterate old fish back to young since they're spawning
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_bigSchool[ResetFishAge] += toSpawn
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// Spawn the new fish
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efficientSpawn(toSpawn)
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}
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}
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module.exports = {
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school,
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efficientSchool,
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ageFish,
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spawn,
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efficientSpawn
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}

‎2021/day-06/fish.test.js

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/* eslint-env mocha */
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const { expect } = require('chai')
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const { school, ageFish, spawn, efficientSchool, efficientSpawn } = require('./fish')
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describe('--- Day 6: Lanternfish ---', () => {
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describe('Part 1', () => {
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beforeEach(() => {
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// ensure flushed state
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school.state = [3, 4, 3, 1, 2]
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expect(school.state).to.deep.equal([3, 4, 3, 1, 2])
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})
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describe('spawn()', () => {
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it('adds new fish to the end of the list', () => {
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spawn(4)
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expect(school.state).to.deep.equal([3, 4, 3, 1, 2, 8, 8, 8, 8])
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})
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})
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describe('ageFish()', () => {
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it('ages a particular fish', () => {
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expect(ageFish(6)).to.equal(5)
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expect(ageFish(5)).to.equal(4)
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expect(ageFish(4)).to.equal(3)
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expect(ageFish(3)).to.equal(2)
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expect(ageFish(2)).to.equal(1)
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expect(ageFish(1)).to.equal(0)
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expect(ageFish(0)).to.equal(6)
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expect(ageFish(8)).to.equal(7)
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expect(ageFish(7)).to.equal(6)
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})
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it('throws an error if the fish is out of range', () => {
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expect(() => { ageFish(9) }).to.throw('Fish is too young')
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expect(() => { ageFish(-1) }).to.throw('Fish is too old')
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})
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})
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describe('advance()', () => {
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it('advances one day', () => {
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school.state = [3, 4, 3, 1, 2]
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school.advance()
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expect(school.state).to.deep.equal([2, 3, 2, 0, 1])
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school.advance()
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expect(school.state).to.deep.equal([1, 2, 1, 6, 0, 8])
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school.advance()
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expect(school.state).to.deep.equal([0, 1, 0, 5, 6, 7, 8])
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school.advance()
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expect(school.state).to.deep.equal([6, 0, 6, 4, 5, 6, 7, 8, 8])
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school.advance()
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expect(school.state).to.deep.equal([5, 6, 5, 3, 4, 5, 6, 7, 7, 8])
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school.advance()
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expect(school.state).to.deep.equal([4, 5, 4, 2, 3, 4, 5, 6, 6, 7])
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school.advance()
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expect(school.state).to.deep.equal([3, 4, 3, 1, 2, 3, 4, 5, 5, 6])
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school.advance()
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expect(school.state).to.deep.equal([2, 3, 2, 0, 1, 2, 3, 4, 4, 5])
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school.advance()
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expect(school.state).to.deep.equal([1, 2, 1, 6, 0, 1, 2, 3, 3, 4, 8])
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school.advance()
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expect(school.state).to.deep.equal([0, 1, 0, 5, 6, 0, 1, 2, 2, 3, 7, 8])
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school.advance()
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expect(school.state).to.deep.equal([6, 0, 6, 4, 5, 6, 0, 1, 1, 2, 6, 7, 8, 8, 8])
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school.advance()
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expect(school.state).to.deep.equal([5, 6, 5, 3, 4, 5, 6, 0, 0, 1, 5, 6, 7, 7, 7, 8, 8])
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school.advance()
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expect(school.state).to.deep.equal([4, 5, 4, 2, 3, 4, 5, 6, 6, 0, 4, 5, 6, 6, 6, 7, 7, 8, 8])
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school.advance()
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expect(school.state).to.deep.equal([3, 4, 3, 1, 2, 3, 4, 5, 5, 6, 3, 4, 5, 5, 5, 6, 6, 7, 7, 8])
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school.advance()
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expect(school.state).to.deep.equal([2, 3, 2, 0, 1, 2, 3, 4, 4, 5, 2, 3, 4, 4, 4, 5, 5, 6, 6, 7])
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school.advance()
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expect(school.state).to.deep.equal([1, 2, 1, 6, 0, 1, 2, 3, 3, 4, 1, 2, 3, 3, 3, 4, 4, 5, 5, 6, 8])
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school.advance()
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expect(school.state).to.deep.equal([0, 1, 0, 5, 6, 0, 1, 2, 2, 3, 0, 1, 2, 2, 2, 3, 3, 4, 4, 5, 7, 8])
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school.advance()
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expect(school.state).to.deep.equal([6, 0, 6, 4, 5, 6, 0, 1, 1, 2, 6, 0, 1, 1, 1, 2, 2, 3, 3, 4, 6, 7, 8, 8, 8, 8])
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})
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})
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})
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describe('Part 2', () => {
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beforeEach(() => {
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// ensure flushed state
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efficientSchool.state = [3, 4, 3, 1, 2]
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expect(efficientSchool.state).to.deep.equal([0, 1, 1, 2, 1, 0, 0, 0, 0])
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})
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describe('efficientSpawn()', () => {
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it('efficiently adds new fish to the school', () => {
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efficientSpawn(4)
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expect(efficientSchool.state).to.deep.equal([0, 1, 1, 2, 1, 0, 0, 0, 4])
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})
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})
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describe('efficientAdvance', () => {
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it('advances one day following the same pattern without tracking unique position', () => {
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const sum = (x, y) => x + y
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efficientSchool.state = [3, 4, 3, 1, 2]
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([2, 3, 2, 0, 1].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([1, 2, 1, 6, 0, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([0, 1, 0, 5, 6, 7, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([6, 0, 6, 4, 5, 6, 7, 8, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([5, 6, 5, 3, 4, 5, 6, 7, 7, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([4, 5, 4, 2, 3, 4, 5, 6, 6, 7].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([3, 4, 3, 1, 2, 3, 4, 5, 5, 6].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([2, 3, 2, 0, 1, 2, 3, 4, 4, 5].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([1, 2, 1, 6, 0, 1, 2, 3, 3, 4, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([0, 1, 0, 5, 6, 0, 1, 2, 2, 3, 7, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([6, 0, 6, 4, 5, 6, 0, 1, 1, 2, 6, 7, 8, 8, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([5, 6, 5, 3, 4, 5, 6, 0, 0, 1, 5, 6, 7, 7, 7, 8, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([4, 5, 4, 2, 3, 4, 5, 6, 6, 0, 4, 5, 6, 6, 6, 7, 7, 8, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([3, 4, 3, 1, 2, 3, 4, 5, 5, 6, 3, 4, 5, 5, 5, 6, 6, 7, 7, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([2, 3, 2, 0, 1, 2, 3, 4, 4, 5, 2, 3, 4, 4, 4, 5, 5, 6, 6, 7].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([1, 2, 1, 6, 0, 1, 2, 3, 3, 4, 1, 2, 3, 3, 3, 4, 4, 5, 5, 6, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([0, 1, 0, 5, 6, 0, 1, 2, 2, 3, 0, 1, 2, 2, 2, 3, 3, 4, 4, 5, 7, 8].length)
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efficientSchool.advance()
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expect(efficientSchool.state.reduce(sum)).to.equal([6, 0, 6, 4, 5, 6, 0, 1, 1, 2, 6, 0, 1, 1, 1, 2, 2, 3, 3, 4, 6, 7, 8, 8, 8, 8].length)
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})
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it('advances efficiently for a large number of days', () => {
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efficientSchool.state = [3, 4, 3, 1, 2]
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for (let d = 1; d <= 256; d++) {
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efficientSchool.advance()
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}
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const sum = (x, y) => x + y
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efficientSchool.state.reduce(sum)
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})
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})
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})
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})

‎2021/day-06/index.js

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// eslint-disable-next-line no-unused-vars
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const console = require('../helpers')
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require('./solution')

‎2021/day-06/input.txt

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1,1,3,5,1,3,2,1,5,3,1,4,4,4,1,1,1,3,1,4,3,1,2,2,2,4,1,1,5,5,4,3,1,1,1,1,1,1,3,4,1,2,2,5,1,3,5,1,3,2,5,2,2,4,1,1,1,4,3,3,3,1,1,1,1,3,1,3,3,4,4,1,1,5,4,2,2,5,4,5,2,5,1,4,2,1,5,5,5,4,3,1,1,4,1,1,3,1,3,4,1,1,2,4,2,1,1,2,3,1,1,1,4,1,3,5,5,5,5,1,2,2,1,3,1,2,5,1,4,4,5,5,4,1,1,3,3,1,5,1,1,4,1,3,3,2,4,2,4,1,5,5,1,2,5,1,5,4,3,1,1,1,5,4,1,1,4,1,2,3,1,3,5,1,1,1,2,4,5,5,5,4,1,4,1,4,1,1,1,1,1,5,2,1,1,1,1,2,3,1,4,5,5,2,4,1,5,1,3,1,4,1,1,1,4,2,3,2,3,1,5,2,1,1,4,2,1,1,5,1,4,1,1,5,5,4,3,5,1,4,3,4,4,5,1,1,1,2,1,1,2,1,1,3,2,4,5,3,5,1,2,2,2,5,1,2,5,3,5,1,1,4,5,2,1,4,1,5,2,1,1,2,5,4,1,3,5,3,1,1,3,1,4,4,2,2,4,3,1,1

‎2021/day-06/solution.js

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const fs = require('fs')
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const path = require('path')
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const filePath = path.join(__dirname, 'input.txt')
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const { parseData } = require('../../2018/inputParser')
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const { school, efficientSchool } = require('./fish')
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fs.readFile(filePath, { encoding: 'utf8' }, (err, initData) => {
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if (err) throw err
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initData = parseData(initData.trim())
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const resetInput = () => {
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// Deep copy to ensure we aren't mutating the original data
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return JSON.parse(JSON.stringify(initData))
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}
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const part1 = () => {
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const data = resetInput()
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school.state = data
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// Advance the designated time
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for (let x = 0; x < 80; x++) {
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school.advance()
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}
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// Count how many fish we have
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return school.state.length
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}
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const part2 = () => {
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const data = resetInput()
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efficientSchool.state = data
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// Advance the designated time
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for (let x = 0; x < 256; x++) {
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efficientSchool.advance()
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}
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// Count how many fish we have
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const sum = (x, y) => x + y
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return efficientSchool.state.reduce(sum)
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}
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const answers = []
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answers.push(part1())
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answers.push(part2())
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answers.forEach((ans, idx) => {
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console.info(`-- Part ${idx + 1} --`)
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console.info(`Answer: ${ans}`)
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})
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})

‎index.js

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require('./2021/day-05/solution')
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require('./2021/day-06/solution')

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