feat(2019-day-03): utilities for finding wire intersections

developher-net · developher-net · commit 5c567f689990 · 2019-12-13T10:59:22.000-08:00
diff --git a/2019/day-03/wires.js b/2019/day-03/wires.js
@@ -0,0 +1,58 @@
+const intersection = require('path-intersection')
+const { distance } = require('../../2018/day-06/coordinates') // Manhattan distance function from last year
+
+const elfWireToSVGPath = (path) => {
+  const replacements = {
+    R: 'h', // R(ight) becomes relative positive horizontal lineto
+    L: 'h-', // L(eft) becomes relative negative horizontal lineto
+    U: 'v-', // U(p) becomes relative negative vertical line
+    D: 'v', // D(own) becomes relative positive vertical line
+    ',': ' ' // Separators are done with whitespace
+  }
+  path = path.trim()
+
+  const pattern = new RegExp(Object.keys(replacements).join('|'), 'gi')
+  path = path.replace(pattern, (match) => {
+    return replacements[match]
+  })
+
+  return `M0,0 ${path}`
+}
+
+const findWireIntersections = (wires) => {
+  wires = wires.map(elfWireToSVGPath)
+  const ints = intersection(
+    ...wires
+  ).map((point) => {
+    return { x: parseInt(point.x), y: parseInt(point.y) }
+  })
+
+  return ints.sort(isCloser)
+}
+
+const isCloser = (intA, intB) => {
+  const origin = { x: 0, y: 0 }
+  intA.distance = distance(origin, intA)
+  intB.distance = distance(origin, intB)
+  if (intA.distance < intB.distance) {
+    return -1
+  }
+  if (intA.distance > intB.distance) {
+    return 1
+  }
+  if (intA.distance === intB.distance) {
+    return 0
+  }
+}
+
+const getClosesetIntersection = (intersections) => {
+  intersections.sort(isCloser)
+  // Skip the origin since all wires start at origin
+  return intersections[1]
+}
+
+module.exports = {
+  elfWireToSVGPath,
+  findWireIntersections,
+  getClosesetIntersection
+}
diff --git a/package-lock.json b/package-lock.json
diff --git a/package.json b/package.json
@@ -5,6 +5,7 @@
   "main": "index.js",
   "private": true,
   "scripts": {
+    "start": "node index.js",
     "pretest": "npm run lint",
     "test": "nyc mocha \"./20*/**/*.test.js\"",
     "posttest": "nyc report --reporter=html --reporter=text-lcov > coverage.lcov",
@@ -35,5 +36,8 @@
     "nyc": "^14.1.1",
     "semantic-release": "^15.13.31",
     "standard": "^14.3.1"
+  },
+  "dependencies": {
+    "path-intersection": "^2.0.1"
   }
 }
