use a heap for marginally faster execution

day16/d16p1.swift

@@ -111,10 +111,10 @@ struct Maze : CustomStringConvertible {
         let edges = graph()
         // edges.forEach { k, v in print(" - \(k): \(v)") }
 
-        var q: [CellCost] = [(cell: start, cost: 0)]
+        var q = Heap<CellCost>(comparator: { $0.cost < $1.cost })
+        q.insert((cell: start, cost: 0))
         var visited: [Cell:Int] = [:]
-        while !q.isEmpty {
-            let e = q.removeLast()
+        while let e = q.pop() {
             if let node = edges[e.cell] {
                 for (cell, cost) in node {
                     if let prevCost = visited[cell] {
@@ -123,7 +123,7 @@ struct Maze : CustomStringConvertible {
                         }
                     }
                     visited[cell] = e.cost + cost
-                    q.append((cell: cell, cost: e.cost + cost))
+                    q.insert((cell: cell, cost: e.cost + cost))
                 }
             }
         }
@@ -131,6 +131,12 @@ struct Maze : CustomStringConvertible {
     }
 }
 
-let maze = try Maze(fromFile: CommandLine.arguments[1])
-// print(maze)
-print(maze.search())
+@main
+struct AoC {
+    static func main() throws {
+        let maze = try Maze(fromFile: CommandLine.arguments[1])
+        // print(maze)
+        print(maze.search())
+    }
+}
+