feat(2020-day-06): calculate checksum of a given group's answers

Author: developher-net

2020/day-06/questions.js

@@ -0,0 +1,17 @@
+const alphabet = [...'abcdefghijklmnopqrstuvwxyz']
+
+/**
+ * Counts which questions were answered by
+ * at least one passenger in the group.
+ * Multiple people answering doesn't matter.
+ */
+const groupChecksum = (answers) => {
+  return alphabet.reduce((sum, ltr) => {
+    if (String(answers).includes(ltr)) { sum++ }
+    return sum
+  }, 0)
+}
+
+module.exports = {
+  groupChecksum
+}

2020/day-06/questions.test.js

@@ -0,0 +1,35 @@
+/* eslint-env mocha */
+const { expect } = require('chai')
+const { groupChecksum } = require('./questions')
+
+const testData = {
+  groups: [
+    `abcx
+      abcy
+      abcz`,
+    'abc',
+    `a
+      b
+      c`,
+    `ab
+      ac`,
+    `a
+      a
+      a
+      a`,
+    'b'
+  ],
+  checksums: [6, 3, 3, 3, 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])
+        })
+      })
+    })
+  })
+})