[2] realising BFS DFS and A*

lukovnikovde/docs/data/2-nd-exercise/main.py

@@ -1,5 +1,9 @@
 import sys
 import os
+from collections import deque
+import heapq
+import time
+
 
 class Tile:
     """Клетка лабиринта."""
@@ -92,26 +96,125 @@ class TextLabyrinthLoader(LabyrinthLoader):
         return lab
 
 
-if __name__ == "__main__":
+class Pathfinder:
-    # Простая проверка загрузки и вывода лабиринта
+    def find_path(self, lab, start, goal):
-    loader = TextLabyrinthLoader()
+        raise NotImplementedError
-    lab = loader.load("maze/maze1.txt")   # временно создадим позже
 
-    os.system('cls' if os.name == 'nt' else 'clear')
+    def _build_path(self, came_from, start, goal):
-    print("=" * (lab.width * 2 + 4))
+        path = []
-    print("   ЛАБИРИНТ (загружен)")
+        cur = goal
-    print("=" * (lab.width * 2 + 4))
+        while cur is not None:
-    for y in range(lab.height):
+            path.append(cur)
-        print("  ", end='')
+            cur = came_from.get(cur)
-        for x in range(lab.width):
+        path.reverse()
-            t = lab.get_tile(x, y)
+        return path
-            if t == lab.start_tile:
+
-                print('S', end=' ')
+    def visited_count(self):
-            elif t == lab.exit_tile:
+        return getattr(self, '_visited', 0)
-                print('E', end=' ')
+
-            elif t.wall:
+
-                print('#', end=' ')
+class BFS(Pathfinder):
+    def find_path(self, lab, start, goal):
+        q = deque([start])
+        parent = {start: None}
+        visited = {start}
+        while q:
+            cur = q.popleft()
+            if cur == goal:
+                self._visited = len(visited)
+                return self._build_path(parent, start, goal)
+            for nb in lab.neighbours(cur):
+                if nb not in visited:
+                    visited.add(nb)
+                    parent[nb] = cur
+                    q.append(nb)
+        self._visited = len(visited)
+        return []
+
+
+class DFS(Pathfinder):
+    def find_path(self, lab, start, goal):
+        stack = [start]
+        parent = {start: None}
+        visited = {start}
+        while stack:
+            cur = stack.pop()
+            if cur == goal:
+                self._visited = len(visited)
+                return self._build_path(parent, start, goal)
+            for nb in lab.neighbours(cur):
+                if nb not in visited:
+                    visited.add(nb)
+                    parent[nb] = cur
+                    stack.append(nb)
+        self._visited = len(visited)
+        return []
+
+
+class AStar(Pathfinder):
+    def _heuristic(self, a, b):
+        return abs(a.x - b.x) + abs(a.y - b.y)
+
+    def find_path(self, lab, start, goal):
+        heap = []
+        counter = 0
+        start_f = self._heuristic(start, goal)
+        heapq.heappush(heap, (start_f, counter, start))
+        counter += 1
+        parent = {}
+        g = {start: 0}
+        f = {start: start_f}
+        visited = set()
+        while heap:
+            cur_f, _, cur = heapq.heappop(heap)
+            visited.add(cur)
+            if cur == goal:
+                self._visited = len(visited)
+                return self._build_path(parent, start, goal)
+            if cur_f > f.get(cur, float('inf')):
+                continue
+            for nb in lab.neighbours(cur):
+                new_g = g[cur] + 1
+                if new_g < g.get(nb, float('inf')):
+                    parent[nb] = cur
+                    g[nb] = new_g
+                    new_f = new_g + self._heuristic(nb, goal)
+                    f[nb] = new_f
+                    heapq.heappush(heap, (new_f, counter, nb))
+                    counter += 1
+        self._visited = len(visited)
+        return []
+
+
+class LabyrinthSolver:
+    def __init__(self, lab):
+        self.lab = lab
+        self.strategy = None
+
+    def set_strategy(self, strategy):
+        self.strategy = strategy
+
+    def solve(self):
+        if not self.strategy:
+            return None
+        t0 = time.perf_counter()
+        path = self.strategy.find_path(self.lab, self.lab.start_tile, self.lab.exit_tile)
+        t1 = time.perf_counter()
+        return {
+            'time_ms': (t1 - t0) * 1000,
+            'visited': self.strategy.visited_count(),
+            'length': len(path)
+        }
+
+
+if __name__ == "__main__":
+    loader = TextLabyrinthLoader()
+    lab = loader.load("maze/maze1.txt")
+    print("Загружен лабиринт, пробуем BFS...")
+    solver = LabyrinthSolver(lab)
+    solver.set_strategy(BFS())
+    stats = solver.solve()
+    if stats['length'] > 0:
+        print(f"BFS: время={stats['time_ms']:.3f}мс, посещено={stats['visited']}, длина={stats['length']}")
     else:
-                print('.', end=' ')
+        print("Путь не найден")
-        print()
-    print("=" * (lab.width * 2 + 4))