feat: solve advent of code 2016 day 1 part 2

Author: JCPedroza

src/advent-of-code/2016/01-no-time-for-a-taxicab/part-a/ntfta.test.js

@@ -10,7 +10,7 @@ const bigInputPath = join(__dirname, '../input-big.txt')
 const bigInput = readFileSync(bigInputPath, 'utf-8')
 
 for (const { fun, id } of solutions) {
-  describe(`Advent of Code 'No Time for a Taxicab' solution '${id}'`, () => {
+  describe(`Advent of Code 'No Time for a Taxicab p1' solution '${id}'`, () => {
     it('solves for empty directions', () => {
       assert.equal(fun(''), 0)
     })

src/advent-of-code/2016/01-no-time-for-a-taxicab/part-b/ntftb-num-map-set.js

@@ -0,0 +1,60 @@
+/**
+ * Finds the block distance from the first repeated location. Uses maps
+ * numbers to number set to remember locations.
+ *
+ * @param {string} instr
+ * @returns {number}
+ */
+const blockDistance = (instr) => {
+  let x = 0
+  let y = 0
+  let dir = 0 // 0: north, 1: east, 2: south, 3: west
+
+  /** @type {Map<number, Set<number>>} */
+  const pastLocs = new Map()
+  const splitIns = instr ? instr.split(', ') : []
+
+  for (const ins of splitIns) {
+    const turn = ins[0]
+    const dist = parseInt(ins.slice(1))
+    let prevX = x
+    let prevY = y
+
+    // Update direction based on turn.
+    if (turn === 'L') dir = (dir + 3) % 4
+    else dir = (dir + 1) % 4
+
+    // Update distance based on direction.
+    if (dir === 0) y += dist
+    else if (dir === 1) x += dist
+    else if (dir === 2) y -= dist
+    else x -= dist
+
+    // Remember all visited locations on the x axis.
+    while (prevX !== x) {
+      if (!pastLocs.has(prevX)) pastLocs.set(prevX, new Set([y]))
+      else if (!pastLocs.get(prevX)?.has(y)) pastLocs.get(prevX)?.add(y)
+      else return Math.abs(prevX) + Math.abs(y)
+
+      if (prevX < x) prevX++
+      else prevX--
+    }
+
+    // Remember all visited locations on the y axis.
+    while (prevY !== y) {
+      if (!pastLocs.has(x)) pastLocs.set(x, new Set([prevY]))
+      else if (!pastLocs.get(x)?.has(prevY)) pastLocs.get(x)?.add(prevY)
+      else return Math.abs(x) + Math.abs(prevY)
+
+      if (prevY < y) prevY++
+      else prevY--
+    }
+  }
+
+  throw new Error('No location was visited more than once')
+}
+
+module.exports = {
+  fun: blockDistance,
+  id: 'number-map-set'
+}

src/advent-of-code/2016/01-no-time-for-a-taxicab/part-b/ntftb-str-set.js

@@ -0,0 +1,46 @@
+/**
+ * Finds the block distance from the first repeated location. Uses one string
+ * set to remember locations.
+ *
+ * Time complexity: O(n)
+ * Space complexity: O(n)
+ *
+ * @param {string} instr
+ * @returns {number} Block distance to the first repeated location.
+ */
+const blockDistance = (instr) => {
+  let x = 0
+  let y = 0
+  let dir = 0 // 0: north, 1: east, 2: south, 3: west
+
+  const splitIns = instr ? instr.split(', ') : []
+  const pastLocs = new Set(`${x},${y}`)
+
+  for (const ins of splitIns) {
+    const turn = ins[0]
+    const dist = parseInt(ins.slice(1))
+
+    // Update direction based on turn.
+    if (turn === 'L') dir = (dir + 3) % 4
+    else dir = (dir + 1) % 4
+
+    for (let block = 0; block < dist; block++) {
+      if (dir === 0) y++
+      else if (dir === 1) x++
+      else if (dir === 2) y--
+      else x--
+
+      const strLoc = `${x},${y}`
+      if (pastLocs.has(strLoc)) return Math.abs(x) + Math.abs(y)
+
+      pastLocs.add(strLoc)
+    }
+  }
+
+  throw new Error('No location was visited more than once')
+}
+
+module.exports = {
+  fun: blockDistance,
+  id: 'str-set'
+}

src/advent-of-code/2016/01-no-time-for-a-taxicab/part-b/ntftb.repo.js

@@ -0,0 +1,9 @@
+const ntftbNumMapSet = require('./ntftb-num-map-set')
+const ntftbStrSet = require('./ntftb-str-set')
+
+const solutions = [
+  ntftbNumMapSet,
+  ntftbStrSet
+]
+
+module.exports = solutions

src/advent-of-code/2016/01-no-time-for-a-taxicab/part-b/ntftb.test.js

@@ -0,0 +1,30 @@
+const { describe, it } = require('node:test')
+const assert = require('node:assert/strict')
+
+const { readFileSync } = require('fs')
+const { join } = require('path')
+
+const solutions = require('./ntftb.repo')
+
+const bigInputPath = join(__dirname, '../input-big.txt')
+const bigInput = readFileSync(bigInputPath, 'utf-8')
+
+for (const { fun, id } of solutions) {
+  describe(`Advent of Code 'No Time for a Taxicab p2' solution '${id}'`, () => {
+    it('throws for empty directions', () => {
+      assert.throws(() => fun(''))
+    })
+
+    it('throws for directions without solution', () => {
+      assert.throws(() => fun('R2, L2, R2, L2'))
+    })
+
+    it('solves for four directions', () => {
+      assert.equal(fun('R8, R4, R4, R8'), 4)
+    })
+
+    it('solves big-sized directions (solves the puzzle)', () => {
+      assert.equal(fun(bigInput), 182)
+    })
+  })
+}

src/advent-of-code/2016/01-no-time-for-a-taxicab/part-b/ntftb.time.js

@@ -0,0 +1,14 @@
+const { readFileSync } = require('fs')
+const { join } = require('path')
+
+const { timeAndReport } = require('../../../../../lib/time')
+const solutions = require('./ntftb.repo')
+
+const bigInputPath = join(__dirname, '../input-huge.txt')
+const bigInput = readFileSync(bigInputPath, 'utf-8')
+
+const args = [bigInput]
+const runs = 10_000
+const id = 'Advent of Code 2016 day 1 part 2'
+
+timeAndReport(solutions, args, runs, id)