developher-net · developher-net · Dec 14, 2021 · Dec 14, 2021 · Dec 14, 2021
diff --git a/2021/day-03/engineDiagnostics.js b/2021/day-03/engineDiagnostics.js
@@ -0,0 +1,86 @@
+/**
+ * Find the most common bit at a position
+ * @param [str] data
+ * @param int position
+ */
+const getMostCommon = (data, position) => {
+  const offs = data.filter((reading) => {
+    return reading[position] === '0'
+  }).length
+  // there can only be 2 values, so easy to check which has more as being above 50%
+  return (offs > data.length / 2) ? '0' : '1'
+}
+
+/**
+ * Find the least common bit at a position
+ * @param [str] data
+ * @param int position
+ */
+const getLeastCommon = (data, position) => {
+  return (getMostCommon(data, position) === '0') ? '1' : '0'
+}
+
+/**
+ * Calc the gamma value of the data set
+ * @param [str] data
+ */
+const getGamma = (data) => {
+  let gamma = ''
+  for (let x = 0; x < data[0].length; x++) {
+    gamma += getMostCommon(data, x)
+  }
+  return gamma
+}
+
+const getEpsilon = (data) => {
+  let epsilon = ''
+  for (let x = 0; x < data[0].length; x++) {
+    epsilon += getLeastCommon(data, x)
+  }
+  return epsilon
+}
+
+const getO2 = (data) => {
+  return getAir(data, getMostCommon)
+}
+
+const getCO2 = (data) => {
+  return getAir(data, getLeastCommon)
+}
+
+const getAir = (data, filterMethod) => {
+  let dataset = data
+  // Loop through each digit, find the most common bit for that digit, and filter
+  // out any readings that don't share that digit
+  //
+  // TODO: Probably faster with bitmap math, but .... ehh... runs fast enough
+  for (let x = 0; x < data[0].length; x++) {
+    if (dataset.length > 1) {
+      const bit = filterMethod(dataset, x)
+      dataset = dataset.filter((reading) => {
+        return reading[x] === bit
+      })
+    }
+  }
+
+  if (dataset.length > 1) {
+    throw new Error(`Found too many results ${dataset}`)
+  }
+
+  return dataset[0]
+}
+
+const calcPowerConsumption = (gamma, epsilon) => {
+  return parseInt(gamma, 2) * parseInt(epsilon, 2)
+}
+
+module.exports = {
+  getGamma,
+  getEpsilon,
+  getMostCommon,
+  getLeastCommon,
+  getO2,
+  getCO2,
+  calcPowerConsumption,
+  calcLifeSupport: calcPowerConsumption
+}
diff --git a/2021/day-03/engineDiagnostics.test.js b/2021/day-03/engineDiagnostics.test.js
@@ -0,0 +1,73 @@
+/* eslint-env mocha */
+const { expect } = require('chai')
+const { getMostCommon, getLeastCommon, getEpsilon, getGamma, getO2, getCO2, calcPowerConsumption, calcLifeSupport } = require('./engineDiagnostics')
+
+const testData = [
+  '00100',
+  '11110',
+  '10110',
+  '10111',
+  '10101',
+  '01111',
+  '00111',
+  '11100',
+  '10000',
+  '11001',
+  '00010',
+  '01010'
+]
+
+describe('--- Day 3: Binary Diagnostic ---', () => {
+  describe('Part 1', () => {
+    describe('getMostCommon()', () => {
+      it('finds the most common bit at a position', () => {
+        expect(getMostCommon(testData, 0)).to.equal('1')
+        expect(getMostCommon(testData, 1)).to.equal('0')
+        expect(getMostCommon(testData, 2)).to.equal('1')
+        expect(getMostCommon(testData, 3)).to.equal('1')
+        expect(getMostCommon(testData, 4)).to.equal('0')
+      })
+    })
+    describe('getLeastCommon()', () => {
+      it('finds the least common bit at a position', () => {
+        expect(getLeastCommon(testData, 0)).to.equal('0')
+        expect(getLeastCommon(testData, 1)).to.equal('1')
+        expect(getLeastCommon(testData, 2)).to.equal('0')
+        expect(getLeastCommon(testData, 3)).to.equal('0')
+        expect(getLeastCommon(testData, 4)).to.equal('1')
+      })
+    })
+    describe('getGamma()', () => {
+      it('finds the gamma rate from the provided data using the most common bits in each position', () => {
+        expect(getGamma(testData)).to.equal('10110')
+      })
+    })
+    describe('getEpsilon()', () => {
+      it('finds the epsilon rate from the provided data using the least common bits in each position', () => {
+        expect(getEpsilon(testData)).to.equal('01001')
+      })
+    })
+    describe('calcPowerConsumption', () => {
+      it('calculates the power consumption by multiplying the gamma and epsilon rates as decimals', () => {
+        expect(calcPowerConsumption('10110', '01001')).to.equal(198)
+      })
+    })
+  })
+  describe('Part 2', () => {
+    describe('getO2()', () => {
+      it('calculates the oxygen generator rating from the provided data', () => {
+        expect(getO2(testData)).to.equal('10111')
+      })
+    })
+    describe('getCO2()', () => {
+      it('calculates the carbon dioxide scrubber rating from the provided data', () => {
+        expect(getCO2(testData)).to.equal('01010')
+      })
+    })
+    describe('calcLifeSupport', () => {
+      it('calculates the life support rating by multiplying the O2 and C02 rates rates as decimals', () => {
+        expect(calcLifeSupport('10110', '01001')).to.equal(198)
+      })
+    })
+  })
+})
diff --git a/2021/day-03/index.js b/2021/day-03/index.js
@@ -0,0 +1,3 @@
+// eslint-disable-next-line no-unused-vars
+const console = require('../helpers')
+require('./solution')