feat(2021-day-02): move the submarine using aiming

developher-net · developher-net · commit 43985c85baef · 2021-12-13T17:53:29.000-08:00
diff --git a/2021/day-02/navigate.js b/2021/day-02/navigate.js
@@ -16,15 +16,39 @@ const move = (location, direction, distance) => {
   return result
 }
 
-const navigate = (location, route) => {
+const navigate = (location, route, useAiming = false) => {
   let position = location
   route.forEach(instruction => {
-    position = move(position, instruction[0], instruction[1])
+    if (useAiming) {
+      position = aimedMove(position, instruction[0], instruction[1])
+    } else {
+      position = move(position, instruction[0], instruction[1])
+    }
   })
   return position
 }
 
+const aimedMove = (location, direction, distance) => {
+  const result = location
+  switch (direction) {
+    case 'forward':
+      result.x += distance
+      result.d += (distance * location.a)
+      break
+    case 'up':
+      result.a -= distance
+      break
+    case 'down':
+      result.a += distance
+      break
+    default:
+      throw new Error(`Direction ${direction} is unsupported`)
+  }
+  return result
+}
+
 module.exports = {
   move,
-  navigate
+  navigate,
+  aimedMove
 }
diff --git a/2021/day-02/navigate.test.js b/2021/day-02/navigate.test.js
@@ -1,6 +1,6 @@
 /* eslint-env mocha */
 const { expect } = require('chai')
-const { move, navigate } = require('./navigate')
+const { move, navigate, aimedMove } = require('./navigate')
 
 const TestRoute = [
   ['forward', 5],
@@ -47,4 +47,48 @@ describe('--- Day 2: Dive! ---', () => {
       })
     })
   })
+  describe('Part 2', () => {
+    describe('aimedMove()', () => {
+      it('moves forward when the aim is 0', () => {
+        expect(aimedMove({ x: 0, d: 0, a: 0 }, 'forward', 5)).to.deep.equal({
+          x: 5,
+          d: 0,
+          a: 0
+        })
+      })
+      it('aims down without moving', () => {
+        expect(aimedMove({ x: 0, d: 0, a: 0 }, 'down', 5)).to.deep.equal({
+          x: 0,
+          d: 0,
+          a: 5
+        })
+      })
+      it('moves forward and down when aimed', () => {
+        expect(aimedMove({ x: 0, d: 0, a: 5 }, 'forward', 8)).to.deep.equal({
+          x: 8,
+          d: 40,
+          a: 5
+        })
+      })
+      it('aims up without moving', () => {
+        expect(aimedMove({ x: 0, d: 0, a: 5 }, 'up', 3)).to.deep.equal({
+          x: 0,
+          d: 0,
+          a: 2
+        })
+      })
+      it('throws an error for an unexpected direction', () => {
+        expect(() => {
+          aimedMove({ x: 0, d: 0, a: 5 }, 'garbage', 5)
+        }).to.throw('Direction garbage is unsupported')
+      })
+    })
+    describe('navigate()', () => {
+      it('can navigate using aiming', () => {
+        const destination = navigate({ x: 0, d: 0, a: 0 }, TestRoute, true)
+        expect(destination.x).to.equal(15)
+        expect(destination.d).to.equal(60)
+      })
+    })
+  })
 })
diff --git a/2021/day-02/solution.js b/2021/day-02/solution.js
@@ -28,8 +28,8 @@ fs.readFile(filePath, { encoding: 'utf8' }, (err, initData) => {
 
   const part2 = () => {
     const data = resetInput()
-    console.debug(data)
-    return 'No answer yet'
+    const destination = navigate({ x: 0, d: 0, a: 0 }, data, true)
+    return destination.x * destination.d
   }
   const answers = []
   answers.push(part1())
