feat(2021-day-01): use a sampled depth measurement for depth calculations

developher-net · developher-net · commit 4f34c30ef661 · 2021-12-13T16:46:45.000-08:00
Solves part #2
diff --git a/2021/day-01/solution.js b/2021/day-01/solution.js
@@ -2,7 +2,7 @@ const fs = require('fs')
 const path = require('path')
 const filePath = path.join(__dirname, 'input.txt')
 const { inputToArray } = require('../../2018/inputParser')
-const { countIncreasingDepth } = require('./sonarSweep')
+const { countIncreasingDepth, countIncreasingSampledDepth } = require('./sonarSweep')
 
 fs.readFile(filePath, { encoding: 'utf8' }, (err, initData) => {
   if (err) throw err
@@ -21,8 +21,7 @@ fs.readFile(filePath, { encoding: 'utf8' }, (err, initData) => {
 
   const part2 = () => {
     const data = resetInput()
-    console.debug(data)
-    return 'No answer yet'
+    return countIncreasingSampledDepth(data)
   }
   const answers = []
   answers.push(part1())
diff --git a/2021/day-01/sonarSweep.js b/2021/day-01/sonarSweep.js
@@ -17,6 +17,37 @@ const countIncreasingDepth = (pings) => {
   return result
 }
 
+const sampledDepth = (depths, target) => {
+  // console.debug(`sum of ${depths[target]} + ${depths[target + 1]} + ${depths[target + 2]}`)
+  return depths[target] + depths[target + 1] + depths[target + 2]
+}
+
+const countIncreasingSampledDepth = (pings) => {
+  const result = pings.reduce((total, curr, idx, pings) => {
+    // skip first
+    if (idx <= 0) {
+      return 0
+    }
+
+    // Skip measureent if inusfficient remaining samples
+    if (pings.length - idx < 3) {
+      return total
+    }
+
+    // Increment count when sampled depth is larger than the previous sampled depth
+    if (sampledDepth(pings, idx) > sampledDepth(pings, idx - 1)) {
+      total++
+      return total
+    }
+
+    // Otherwise don't increase
+    return total
+  }, 0)
+
+  return result
+}
+
 module.exports = {
-  countIncreasingDepth
+  countIncreasingDepth,
+  countIncreasingSampledDepth
 }
diff --git a/2021/day-01/sonarSweep.test.js b/2021/day-01/sonarSweep.test.js
@@ -1,6 +1,6 @@
 /* eslint-env mocha */
 const { expect } = require('chai')
-const { countIncreasingDepth } = require('./sonarSweep')
+const { countIncreasingDepth, countIncreasingSampledDepth } = require('./sonarSweep')
 
 const pings = [
   199,
@@ -19,6 +19,12 @@ const singlePing = [
   199
 ]
 
+const triplePing = [
+  269,
+  260,
+  263
+]
+
 describe('--- Day 1: Sonar Sweep ---', () => {
   describe('Part 1', () => {
     describe('countIncreasingDepth()', () => {
@@ -31,4 +37,20 @@ describe('--- Day 1: Sonar Sweep ---', () => {
       })
     })
   })
+
+  describe('Part 2', () => {
+    describe('countIncreasingSampledDepth()', () => {
+      it('counts how many times the depth increases between two sequential measurements in an array with measurments averaged over 3 samples', () => {
+        expect(countIncreasingSampledDepth(pings)).to.equal(5)
+      })
+
+      it('skips the first measurement since there are no previous', () => {
+        expect(countIncreasingSampledDepth(singlePing)).to.equal(0)
+      })
+
+      it('skips the measurements when there aren`t enough values ot measure', () => {
+        expect(countIncreasingSampledDepth(triplePing)).to.equal(0)
+      })
+    })
+  })
 })
