graph-search/src/features/maze/solvers.js

@@ -11,17 +11,97 @@ class Edge {
 }
 
 export function solveByBFS(maze) {
-  // TODO: stub
+  const backpointers = new Map();
+  const worklist = new Queue();
+  worklist.insert(new Edge(undefined, maze.entrance));
+  while (worklist.size > 0) {
+    const workitem = worklist.remove();
+    if (backpointers.has(workitem.to)) {
+      continue;
+    }
+    workitem.to.type = CellType.CONSIDERED;
+    backpointers.set(workitem.to, workitem);
+    if (workitem.to === maze.exit) {
+      const reversedPath = [];
+      for (let current = workitem.to;
+        // cells to CellType.SOLUTION
+        // current.type = CellType.SOLUTION;
+        current !== undefined;
+        current = backpointers.get(current).from) {
+        reversedPath.push(current);
+        current.type = CellType.SOLUTION;
+      }
+      return reversedPath.reverse();
+    }
+    for (const incidence of workitem.to.neighbors) {
+      worklist.insert(new Edge(workitem.to, incidence));
+    }
+  }
+  return undefined;
 }
 
 export function solveByDijkstras(maze) {
-  // TODO: stub
+  const backpointers = new Map();
+  const worklist = new PriorityQueue();
+  worklist.insert(new Edge(undefined, maze.entrance, 0), 0);
+  while (worklist.size > 0) {
+    const workitem = worklist.remove();
+    if (backpointers.has(workitem.to)) {
+      continue;
+    }
+    workitem.to.type = CellType.CONSIDERED;
+    backpointers.set(workitem.to, workitem);
+    if (workitem.to === maze.exit) {
+      const reversedPath = [];
+      for (let current = maze.exit;
+        current !== undefined;
+        current = backpointers.get(current).from) {
+        reversedPath.push(current);
+        current.type = CellType.SOLUTION;
+      }
+      return reversedPath.reverse();
+    }
+    for (const incidence of workitem.to.neighbors) {
+      worklist.insert(
+        new Edge(workitem.to, incidence, workitem.distance + 1),
+        workitem.distance,
+      );
+    }
+  }
+  return undefined;
 }
 
 function heuristic(maze, cell) {
-  return 0; // TODO: stub
+  return Math.abs(maze.exit.x - cell.x) + Math.abs(maze.exit.y - cell.y);
 }
 
 export function solveByAStar(maze) {
-  // TODO: stub
+  const backpointers = new Map();
+  const worklist = new PriorityQueue();
+  worklist.insert(
+    new Edge(undefined, maze.entrance, 0),
+    0 + heuristic(maze, maze.exit),
+  );
+  while (worklist.size > 0) {
+    const workitem = worklist.remove();
+    if (backpointers.has(workitem.to)) {
+      continue;
+    }
+    workitem.to.type = CellType.CONSIDERED;
+    backpointers.set(workitem.to, workitem);
+    if (workitem.to === maze.exit) {
+      for (let current = maze.exit;
+        current !== undefined;
+        current = backpointers.get(current).from) {
+        current.type = CellType.SOLUTION;
+      }
+      return;
+    }
+    for (const neighbor of workitem.to.neighbors) {
+      worklist.insert(
+        new Edge(workitem.to, neighbor, workitem.distance + 1),
+        workitem.distance + 1 + heuristic(maze, neighbor),
+      );
+    }
+  }
 }