Add day 14 solution in Chapel

day14.chpl

@@ -0,0 +1,67 @@
+use IO, Set;
+
+proc parseCoord(s: string) {
+  const (x, _, y) = s.partition(",");
+  return (x : int, y : int);
+}
+
+proc (set((int,int))).draw((x1, y1), (x2, y2)) {
+  for x in (min(x1,x2)..max(x1,x2)) {
+    for y in (min(y1,y2)..max(y1,y2)) {
+      this.add((x,y));
+    }
+  }
+}
+
+iter ((int,int)).nextPositions() {
+  yield this + (0,1);
+  yield this + (-1,1);
+  yield this + (1,1);
+}
+
+var occupied = new set((int, int));
+for line in stdin.lines().strip() {
+  const coords = parseCoord(line.split(" -> "));
+  for idx in 0..#(coords.size-1) {
+    occupied.draw(coords[idx], coords[idx+1]);
+  }
+}
+
+const maxHeight = max reduce [(x, y) in occupied] y;
+const initialPos = (500, 0);
+config const hasWall = false;
+var grainCount = 0;
+
+do {
+  // Start a new grain of sand, but give up if there's already one there.
+  var pos = initialPos;
+  if occupied.contains(pos) then break;
+
+  // Make the grain fall
+  var abyss = false;
+  do {
+    var moved = false;
+    for checkPos in pos.nextPositions() {
+      // Check for falling past the floor
+      if checkPos[1] > maxHeight + 10 {
+        abyss = true;
+        break;
+      }
+      // Try moving, but only if the position is clear and not on the floor.
+      if !occupied.contains(checkPos) &&
+         !(hasWall && checkPos[1] == maxHeight + 2) {
+        pos = checkPos;
+        moved = true;
+        break;
+      }
+    }
+  } while moved;
+
+  // If we stopped because we fell off, don't count the last grain.
+  if !abyss {
+    grainCount += 1;
+    occupied.add(pos);
+  }
+} while !abyss;
+
+writeln(grainCount);