fix(2018 day-13): correct order for intersections is left, straight, right, repeat

Author: developher-net

2018/day-13/tracks.js

@@ -7,6 +7,7 @@ class Track {
     this.cartDirections = ['^', '>', 'v', '<']
     this.collision = false
     this.frame = 0
+    this.interSectionOrder = [-1, 0, 1]
     this.trackTurns = ['\\', '/']
     this.trackTypes = this.trackTurns.concat(['-', '|', '+'])
     this.setLayout(track)
@@ -18,14 +19,19 @@ class Track {
 
   /**
    * Determines the next direction for a cart rotating at an intersection
-   * Order of rotations is left (counterclockwise), straigh, right (clockwise), straight
+   * Order of rotations is left (counterclockwise), straight, right (clockwise)
    * @private
    * @param {Object} cart the cart being turned
    * @returns {String} value of new direction
    */
   _intersect (cart) {
+    const i = this.interSectionOrder
     let l = cart.lastIntersections
-    let r = (l[0] !== 0) ? 0 : l[1] * -1
+
+    // Figure out the new rotation
+    let r = i.indexOf(l[0])
+    r = (r + 1 >= i.length) ? i[0] : i[r + 1]
+
     // Track the intersections
     cart.lastIntersections.pop()
     cart.lastIntersections.splice(0, 0, r)
@@ -105,7 +111,7 @@ class Track {
       output += '\n'
     })
 
-    return output.trim()
+    return output
   }
 
   /**
@@ -120,7 +126,7 @@ class Track {
             x: idx,
             y: idy,
             direction: x,
-            lastIntersections: [0, 1] // Assume the first intersection the cart will turn left
+            lastIntersections: [1, 0] // Assume the first ntersection the cart will turn left
           })
           // Replace the cart on the track with a track segment
           // (Assuming cart initial states aren't on instersections)

2018/day-13/tracks.test.js

@@ -23,12 +23,12 @@ describe('--- Day 13: Mine Cart Madness ---', () => {
           x: 2,
           y: 0,
           direction: '>',
-          lastIntersections: [0, 1]
+          lastIntersections: [1, 0]
         }, {
           x: 9,
           y: 3,
           direction: 'v',
-          lastIntersections: [0, 1]
+          lastIntersections: [1, 0]
         }]
         const track = new Track(data)
         const actual = track.carts
@@ -51,7 +51,7 @@ describe('--- Day 13: Mine Cart Madness ---', () => {
   \\------/   `.trim()
         const track = new Track(test)
         track.advance()
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
         expect(track.frame).to.equal(1)
       })
@@ -62,31 +62,31 @@ describe('--- Day 13: Mine Cart Madness ---', () => {
         const track = new Track(test)
         const expected = `-->-`
         track.moveCart(track.carts[0])
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
       })
       it('moves an individual cart left', () => {
         const test = `--<-`
         const track = new Track(test)
         const expected = `-<--`
         track.moveCart(track.carts[0])
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
       })
       it('moves an individual cart down', () => {
         const test = `|\nv\n|\n|`
         const track = new Track(test)
         const expected = `|\n|\nv\n|`
         track.moveCart(track.carts[0])
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
       })
       it('moves an individual cart up', () => {
         const test = `|\n|\n^\n|`
         const track = new Track(test)
         const expected = `|\n^\n|\n|`
         track.moveCart(track.carts[0])
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
       })
       it('rotates a cart when it enters turns', () => {
@@ -114,7 +114,7 @@ describe('--- Day 13: Mine Cart Madness ---', () => {
           const track = new Track(test)
           track.moveCart(track.carts[0])
           track.moveCart(track.carts[0])
-          const actual = track.display()
+          const actual = track.display().trim()
           expect(actual).to.equal(expected[idx])
         })
       })
@@ -124,32 +124,32 @@ describe('--- Day 13: Mine Cart Madness ---', () => {
         const expected = `---^-`
         track.moveCart(track.carts[0])
         track.moveCart(track.carts[0])
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
       })
-      it('tracks the direction through multiple intersections following the sequential rotation rules: left, straight, right, straight', () => {
+      it('tracks the direction through multiple intersections following the sequential rotation rules: left, straight, right', () => {
         const expected = `
-       ^
-       |
-   +-+-+
+     ^
+     |
+   +-+
    |
    +
    |
 ---+`.trim()
         const test = `
-       |
-       |
-   +-+-+
+     |
+     |
+   +-+
    |
    +
    |
 ->-+`
         const track = new Track(test)
 
-        for (let i = 0; i < 12; i++) {
+        for (let i = 0; i < 10; i++) {
           track.moveCart(track.carts[0])
         }
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
       })
       it('only moves the specified cart', () => {
@@ -158,7 +158,7 @@ describe('--- Day 13: Mine Cart Madness ---', () => {
         const track = new Track(test)
         track.moveCart(track.carts[0])
         track.moveCart(track.carts[0])
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
       })
       it('throws an error if the cart runs off the rails', () => {
@@ -178,7 +178,7 @@ describe('--- Day 13: Mine Cart Madness ---', () => {
           track.moveCart(track.carts[0])
           track.moveCart(track.carts[0])
         } catch (err) {
-          const actual = track.display()
+          const actual = track.display().trim()
           expect(actual).to.equal(expected)
           expect(track.collision).to.deep.equal({ x: 3, y: 0 })
         }
@@ -188,7 +188,7 @@ describe('--- Day 13: Mine Cart Madness ---', () => {
       it('renders the current track state', () => {
         const expected = data.trim()
         const track = new Track(data)
-        const actual = track.display()
+        const actual = track.display().trim()
         expect(actual).to.equal(expected)
       })
     })