feat(2021-day-10): score code autocompletes

2021/day-10/scoring.js

@@ -0,0 +1,27 @@
+
+const findMiddleScore = (scores) => {
+  // According to specs, there's always an odd number of items in the list,
+  // so we're safe to divide by 2 and round down to get the desired index
+  return scores.sort((a, b) => a - b)[
+    Math.floor(scores.length / 2)
+  ]
+}
+
+// How many points each character is worth in autocomplete scoring
+const pointValues = {
+  ')': 1,
+  ']': 2,
+  '}': 3,
+  '>': 4
+}
+
+const scoreAutocomplete = (suggestion) => {
+  return [...suggestion].reduce((score, char) => {
+    return (score * 5) + pointValues[char]
+  }, 0)
+}
+
+module.exports = {
+  findMiddleScore,
+  scoreAutocomplete
+}

2021/day-10/scoring.test.js

@@ -0,0 +1,36 @@
+/* eslint-env mocha */
+const { expect } = require('chai')
+const { findMiddleScore, scoreAutocomplete } = require('./scoring')
+
+const scoreData = [
+  288957,
+  5566,
+  1480781,
+  995444,
+  294
+]
+
+const autocompleteSuggestions = [
+  '}}]])})]',
+  ')}>]})',
+  '}}>}>))))',
+  ']]}}]}]}>',
+  '])}>'
+]
+
+describe('--- Day 10: Syntax Scoring ---', () => {
+  describe('Part 2', () => {
+    describe('scoreAutocomplete()', () => {
+      it('takes a single autocomplete suggestion and scores it', () => {
+        autocompleteSuggestions.forEach((suggestion, idx) => {
+          expect(scoreAutocomplete(suggestion)).to.equal(scoreData[idx])
+        })
+      })
+    })
+    describe('findMiddleScore()', () => {
+      it('takes a list of scores and returns the middle entry after sorting', () => {
+        expect(findMiddleScore(scoreData)).to.equal(288957)
+      })
+    })
+  })
+})