Merge pull request #135 from amclin/feat/2020-day-13

Feat/2020 day 13

Author: developher-net

2020/day-12/ferry.test.js

@@ -3,7 +3,7 @@ const { expect } = require('chai')
 const { distance } = require('../../2018/day-06/coordinates')
 const { move, route } = require('./ferry')
 
-describe('--- Day 11: Seating System ---', () => {
+describe('--- Day 12: Rain Risk ---', () => {
   describe('Part 1', () => {
     describe('move()', () => {
       let origin

2020/day-13/busSchedules.js

@@ -0,0 +1,53 @@
+const parseSchedule = (schedule) => {
+  // Drop "x" and convert to numeric
+  return schedule.split(',').filter((e) => e !== 'x').map(Number)
+}
+
+const findNext = ({ time, schedule }) => {
+  const result = schedule.map((route) => {
+    return {
+      route,
+      wait: route - (time % route)
+    }
+  }).sort(
+    (a, b) => a.wait - b.wait
+  )
+
+  result.forEach((res) => {
+    console.debug(`Wait for route ${res.route} is ${res.wait}`)
+  })
+
+  return result[0]
+}
+
+const findSequentialTime = (schedule) => {
+  const routes = schedule.split(',').map((el) => (el !== 'x') ? Number(el) : el)
+
+  let x = routes[0]
+  let result = []
+  // If we get an array the same length as the routes array, that means all routes matched
+  while (result.length < routes.length) {
+    x += routes[0]
+    // loop through the list looking for el mod = idx
+    let matches = true
+    let i = 0
+    while (i < routes.length && matches === true) {
+      if (routes[i] === 'x') { // "x" doesn't matter
+        i++
+      } else if ((x + i) % routes[i] === 0) { // Route is sequentially +1 above the previous route
+        i++
+      } else {
+        matches = false
+      }
+    }
+    if (matches) { result = routes }
+  }
+  console.debug(`Found a match ${x}`)
+  return x
+}
+
+module.exports = {
+  parseSchedule,
+  findNext,
+  findSequentialTime
+}

2020/day-13/busSchedules.test.js

@@ -0,0 +1,42 @@
+/* eslint-env mocha */
+const { expect } = require('chai')
+const { parseSchedule, findNext, findSequentialTime } = require('./busSchedules')
+
+const testData = {
+  time: 939,
+  schedule: '7,13,x,x,59,x,31,19'
+}
+
+describe('--- Day 13: Shuttle Search ---', () => {
+  describe('Part 1', () => {
+    describe('parseSchedule()', () => {
+      it('cleans up the schedule', () => {
+        expect(parseSchedule(testData.schedule))
+          .to.deep.equal([7, 13, 59, 31, 19])
+      })
+    })
+    describe('findNext()', () => {
+      it('finds the next departing bus', () => {
+        expect(findNext({
+          time: 939,
+          schedule: parseSchedule(testData.schedule)
+        })).to.deep.equal({
+          route: 59,
+          wait: 5
+        })
+      })
+    })
+  })
+  describe('Part 2', () => {
+    describe('findSequentialTime', () => {
+      it('finds a sequential time where the busses all depart sequentially', () => {
+        expect(findSequentialTime('7,13,x,x,59,x,31,19')).to.equal(1068781)
+        expect(findSequentialTime('17,x,13,19')).to.equal(3417)
+        expect(findSequentialTime('67,7,59,61')).to.equal(754018)
+        expect(findSequentialTime('67,x,7,59,61')).to.equal(779210)
+        expect(findSequentialTime('67,7,x,59,61')).to.equal(1261476)
+        expect(findSequentialTime('1789,37,47,1889')).to.equal(1202161486)
+      })
+    })
+  })
+})

2020/day-13/index.js

@@ -0,0 +1,3 @@
+// eslint-disable-next-line no-unused-vars
+const console = require('../helpers')
+require('./solution')

2020/day-13/input.txt

@@ -0,0 +1,2 @@
+1000067
+17,x,x,x,x,x,x,x,x,x,x,37,x,x,x,x,x,439,x,29,x,x,x,x,x,x,x,x,x,x,13,x,x,x,x,x,x,x,x,x,23,x,x,x,x,x,x,x,787,x,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,x,x,19

2020/day-13/solution.js

@@ -0,0 +1,39 @@
+const fs = require('fs')
+const path = require('path')
+const filePath = path.join(__dirname, 'input.txt')
+const { linesToArray } = require('../../2018/inputParser')
+const { parseSchedule, findNext } = require('./busSchedules')
+
+fs.readFile(filePath, { encoding: 'utf8' }, (err, initData) => {
+  if (err) throw err
+
+  initData = linesToArray(initData.trim())
+
+  const resetInput = () => {
+    // Deep copy to ensure we aren't mutating the original data
+    return JSON.parse(JSON.stringify(initData))
+  }
+
+  const part1 = () => {
+    const data = resetInput()
+    const { wait, route } = findNext({
+      time: data[0],
+      schedule: parseSchedule(data[1])
+    })
+    return route * wait
+  }
+
+  const part2 = () => {
+    const data = resetInput()
+    console.debug(data)
+    return 'No answer yet'
+  }
+  const answers = []
+  answers.push(part1())
+  answers.push(part2())
+
+  answers.forEach((ans, idx) => {
+    console.info(`-- Part ${idx + 1} --`)
+    console.info(`Answer: ${ans}`)
+  })
+})