feat(2020-day-06): tally how many questions answered by all users in a group

Author: developher-net

2020/day-06/questions.js

@@ -5,13 +5,32 @@ const alphabet = [...'abcdefghijklmnopqrstuvwxyz']
  * at least one passenger in the group.
  * Multiple people answering doesn't matter.
  */
-const groupChecksum = (answers) => {
+const groupChecksumAnyone = (answers) => {
   return alphabet.reduce((sum, ltr) => {
     if (String(answers).includes(ltr)) { sum++ }
     return sum
   }, 0)
 }
 
+/**
+ * Counts which questions were answered by
+ * all passengers in the group.
+ */
+const groupChecksumEveryone = (answers) => {
+  const results = Object.assign({}, ...alphabet.map(key => ({ [key]: 0 })))
+  const people = answers.trim().split(/[\n\r]+/)
+  people.forEach((person) => {
+    alphabet.forEach((ltr) => {
+      if (String(person).includes(ltr)) { results[ltr]++ }
+    })
+  })
+  // tally the questions where everyone answered
+  return Object.keys(results)
+    .filter((res) => results[res] === people.length)
+    .length
+}
+
 module.exports = {
-  groupChecksum
+  groupChecksum: groupChecksumAnyone,
+  groupChecksumEveryone
 }

2020/day-06/questions.test.js

@@ -1,6 +1,6 @@
 /* eslint-env mocha */
 const { expect } = require('chai')
-const { groupChecksum } = require('./questions')
+const { groupChecksum, groupChecksumEveryone } = require('./questions')
 
 const testData = {
   groups: [
@@ -19,15 +19,25 @@ const testData = {
       a`,
     'b'
   ],
-  checksums: [6, 3, 3, 3, 1, 1]
+  checksumsAnyone: [6, 3, 3, 3, 1, 1],
+  checksumsEveryone: [3, 3, 0, 1, 1, 1]
 }
 
 describe('--- Day 6: Custom Customs ---', () => {
   describe('Part 1', () => {
     describe('groupChecksum()', () => {
       it('tallies the number of unique questions answered collectively by a group', () => {
         testData.groups.forEach((group, idx) => {
-          expect(groupChecksum(group)).to.deep.equal(testData.checksums[idx])
+          expect(groupChecksum(group)).to.deep.equal(testData.checksumsAnyone[idx])
+        })
+      })
+    })
+  })
+  describe('Part 2', () => {
+    describe('groupChecksumEveryone()', () => {
+      it('tallies the number of questions answered by everyone in a group', () => {
+        testData.groups.forEach((group, idx) => {
+          expect(groupChecksumEveryone(group)).to.deep.equal(testData.checksumsEveryone[idx])
         })
       })
     })