Day14: Removal of unneeded HashMap

We don't need to split the tracking of rocks and sand points since we just need to know the amount of rocks we started with and can then subtract this later.

lib/day14.dart

@@ -5,32 +5,31 @@ import 'dart:collection';
 import 'dart:math';
 
 int solveA(Iterable<String> input) {
-  final HashSet<Point<int>> rockPoints = parseRocks(input);
-
-  final int bottomY = rockPoints.reduce((a, b) => a.y > b.y ? a : b).y;
-  final HashSet<Point<int>> sandPoints = HashSet();
+  // A point might be filled with either a rock or sand. In the beginning, we
+  // only have rocks. Since we later need to only count the sand, we keep a
+  // count of how many rocks there are so we can subtract that later.
+  final HashSet<Point<int>> filledPoints = parseRocks(input);
+  final int numberOfRocks = filledPoints.length;
+  final int bottomY = filledPoints.reduce((a, b) => a.y > b.y ? a : b).y;
   const sandSpawnPoint = Point<int>(500, 0);
 
-  bool isNotBlocked(Point<int> point) =>
-      !sandPoints.contains(point) && !rockPoints.contains(point);
-
   outerLoop:
   while (true) {
     var x = sandSpawnPoint.x;
 
     for (var y = sandSpawnPoint.y; y < bottomY; y++) {
       final point = Point(x, y);
 
-      if (isNotBlocked(point.downOneStep)) {
+      if (!filledPoints.contains(point.downOneStep)) {
         // Do nothing since we should just keep going directly down
-      } else if (isNotBlocked(point.oneStepDownAndToTheLeft)) {
+      } else if (!filledPoints.contains(point.oneStepDownAndToTheLeft)) {
         // Move one step to the left
         x--;
-      } else if (isNotBlocked(point.oneStepDownAndToTheRight)) {
+      } else if (!filledPoints.contains(point.oneStepDownAndToTheRight)) {
         // Move one step to the right
         x++;
       } else {
-        sandPoints.add(point);
+        filledPoints.add(point);
         continue outerLoop;
       }
     }
@@ -40,20 +39,17 @@ int solveA(Iterable<String> input) {
     break;
   }
 
-  return sandPoints.length;
+  return filledPoints.length - numberOfRocks;
 }
 
 int solveB(Iterable<String> input) {
-  final HashSet<Point<int>> rockPoints = parseRocks(input);
-
-  final int bottomY = rockPoints.reduce((a, b) => a.y > b.y ? a : b).y + 2;
-  final HashSet<Point<int>> sandPoints = HashSet();
+  final HashSet<Point<int>> filledPoints = parseRocks(input);
+  final int numberOfRocks = filledPoints.length;
+  final int bottomY = filledPoints.reduce((a, b) => a.y > b.y ? a : b).y + 2;
   const sandSpawnPoint = Point<int>(500, 0);
 
   bool isNotBlocked(Point<int> point) =>
-      !sandPoints.contains(point) &&
-      !rockPoints.contains(point) &&
-      point.y < bottomY;
+      !filledPoints.contains(point) && point.y < bottomY;
 
   outerLoop:
   while (isNotBlocked(sandSpawnPoint)) {
@@ -71,13 +67,13 @@ int solveB(Iterable<String> input) {
         // Move one step to the right
         x++;
       } else {
-        sandPoints.add(point);
+        filledPoints.add(point);
         continue outerLoop;
       }
     }
   }
 
-  return sandPoints.length;
+  return filledPoints.length - numberOfRocks;
 }
 
 HashSet<Point<int>> parseRocks(Iterable<String> input) {