feat(2021-day-05): support charting diagonal lines on vent map

2021/day-05/vents.js

@@ -7,7 +7,7 @@
  * @param {*} y2 end of line vertical point
  * @returns
  */
-const chartLine = (data, x1, y1, x2, y2) => {
+const chartLine = (data, x1, y1, x2, y2, allowDiaganol = false) => {
   let x = x1
   let y = y1
   if (y1 === y2) {
@@ -28,6 +28,17 @@ const chartLine = (data, x1, y1, x2, y2) => {
       y += yDir
     }
     data[y][x]++ // coordinates are inclusive
+  } else if (allowDiaganol) {
+    // chart diagonal line
+    console.debug(`Drawing diagonal line ${x1},${y1} to ${x2},${y2}`)
+    const xDir = (x2 > x1) ? 1 : -1
+    const yDir = (y2 > y1) ? 1 : -1
+    while (x !== x2 && y !== y2) {
+      data[y][x]++
+      x += xDir
+      y += yDir
+    }
+    data[y][x]++ // coordinates are inclusive
   } else {
     console.debug(`Skipping diagonal line ${x1},${y1} to ${x2},${y2}`)
   }

2021/day-05/vents.test.js

@@ -24,6 +24,17 @@ const sampleMap = `.......1..
 ..........
 222111....`
 
+const sampleDiagonalMap = `1.1....11.
+.111...2..
+..2.1.111.
+...1.2.2..
+.112313211
+...1.2....
+..1...1...
+.1.....1..
+1.......1.
+222111....`
+
 const parsedTestData = parseLines(testData)
 
 describe('--- Day 5: Hydrothermal Venture ---', () => {
@@ -84,4 +95,19 @@ describe('--- Day 5: Hydrothermal Venture ---', () => {
       })
     })
   })
+  describe('Part 2', () => {
+    describe('chartLine()', () => {
+      it('includes diagonal lines when specified', () => {
+        // 10x10 empty grid
+        let data = [...new Array(10)].map(() => {
+          return [...new Array(10)].map(() => 0)
+        })
+        // Map some lines
+        parsedTestData.forEach((row) => {
+          data = chartLine(data, ...row, true)
+        })
+        expect(render(data)).to.equal(sampleDiagonalMap)
+      })
+    })
+  })
 })