fix(2019-day-03): inconsistent wire intersection lists

developher-net · developher-net · commit 5c169158df10 · 2019-12-13T12:04:38.000-08:00
Shared origin of two wires does not consistently show up in the list of intersections when wires are longer and more complex. See bpmn-io/path-intersection#10
diff --git a/2019/day-03/wires.js b/2019/day-03/wires.js
@@ -47,8 +47,16 @@ const isCloser = (intA, intB) => {
 
 const getClosesetIntersection = (intersections) => {
   intersections.sort(isCloser)
-  // Skip the origin since all wires start at origin
-  return intersections[1]
+
+  // TODO: Remove workaround for bug in SVG intersection library
+  // https://github.com/bpmn-io/path-intersection/issues/10
+  //
+  // The shared origin inconsistently shows up in the intersection list
+  if (parseInt(intersections[0].x) === 0 && parseInt(intersections[0].y) === 0) {
+    // Skip the shared origin since all wires start at origin
+    return intersections[1]
+  }
+  return intersections[0]
 }
 
 module.exports = {
diff --git a/2019/day-03/wires.test.js b/2019/day-03/wires.test.js
@@ -40,5 +40,20 @@ describe('--- 2019 Day 3: Crossed Wires ---', () => {
         expect(actual).to.deep.equal(expected)
       })
     })
+    it('can be used to find the distance to the closest intersection', () => {
+      const wiresets = [
+        [
+          'R75,D30,R83,U83,L12,D49,R71,U7,L72',
+          'U62,R66,U55,R34,D71,R55,D58,R83'
+        ], [
+          'R98,U47,R26,D63,R33,U87,L62,D20,R33,U53,R51',
+          'U98,R91,D20,R16,D67,R40,U7,R15,U6,R7'
+        ]
+      ]
+      const distances = [159, 135]
+      wiresets.forEach((wires, idx) => {
+        expect(getClosesetIntersection(findWireIntersections(wires)).distance).to.equal(distances[idx])
+      })
+    })
   })
 })
diff --git a/index.js b/index.js
@@ -1 +1 @@
-require('./2019/day-02/solution')
+require('./2019/day-03/solution')

Original file line number	Diff line number	Diff line change
`@@ -1 +1 @@`
`1`		`-require('./2019/day-02/solution')`
	`1`	`+require('./2019/day-03/solution')`