diff --git a/komissarovgo/docs2/data2/maze_lab/strategies.py b/komissarovgo/docs2/data2/maze_lab/strategies.py new file mode 100644 index 0000000..c5ff2e6 --- /dev/null +++ b/komissarovgo/docs2/data2/maze_lab/strategies.py @@ -0,0 +1,141 @@ +from abc import ABC, abstractmethod +from collections import deque +import heapq +from typing import List, Dict, Optional +from models import Cell, Maze + + +class PathFindingStrategy(ABC): + + @abstractmethod + def find_path(self, maze: Maze, start: Cell, exit_cell: Cell) -> List[Cell]: + pass + + @property + @abstractmethod + def name(self) -> str: + pass + + +class BFSStrategy(PathFindingStrategy): + + @property + def name(self) -> str: + return "BFS" + + def find_path(self, maze: Maze, start: Cell, exit_cell: Cell) -> List[Cell]: + if start == exit_cell: + return [start] + + queue = deque([start]) + visited = {start} + parent: Dict[Cell, Optional[Cell]] = {start: None} + + while queue: + current = queue.popleft() + + if current == exit_cell: + return self._reconstruct_path(parent, start, exit_cell) + + for neighbor in maze.get_neighbors(current): + if neighbor not in visited: + visited.add(neighbor) + parent[neighbor] = current + queue.append(neighbor) + + return [] + + def _reconstruct_path(self, parent: Dict[Cell, Optional[Cell]], + start: Cell, exit_cell: Cell) -> List[Cell]: + path = [] + current = exit_cell + while current is not None: + path.append(current) + current = parent.get(current) + path.reverse() + return path + + +class DFSStrategy(PathFindingStrategy): + + @property + def name(self) -> str: + return "DFS" + + def find_path(self, maze: Maze, start: Cell, exit_cell: Cell) -> List[Cell]: + if start == exit_cell: + return [start] + + stack = [(start, [start])] + visited = {start} + + while stack: + current, path = stack.pop() + + if current == exit_cell: + return path + + for neighbor in maze.get_neighbors(current): + if neighbor not in visited: + visited.add(neighbor) + stack.append((neighbor, path + [neighbor])) + + return [] + + +class AStarStrategy(PathFindingStrategy): + + @property + def name(self) -> str: + return "A*" + + def _heuristic(self, cell: Cell, target: Cell) -> int: + return abs(cell.x - target.x) + abs(cell.y - target.y) + + def find_path(self, maze: Maze, start: Cell, exit_cell: Cell) -> List[Cell]: + if start == exit_cell: + return [start] + + counter = 0 + open_set = [(0, counter, start)] + came_from: Dict[Cell, Optional[Cell]] = {start: None} + + g_score = {start: 0} + f_score = {start: self._heuristic(start, exit_cell)} + closed_set = set() + + while open_set: + current_f, _, current = heapq.heappop(open_set) + + if current in closed_set: + continue + + if current == exit_cell: + return self._reconstruct_path(came_from, start, exit_cell) + + closed_set.add(current) + + for neighbor in maze.get_neighbors(current): + if neighbor in closed_set: + continue + + tentative_g = g_score[current] + 1 + + if neighbor not in g_score or tentative_g < g_score[neighbor]: + came_from[neighbor] = current + g_score[neighbor] = tentative_g + f_score[neighbor] = tentative_g + self._heuristic(neighbor, exit_cell) + counter += 1 + heapq.heappush(open_set, (f_score[neighbor], counter, neighbor)) + + return [] + + def _reconstruct_path(self, came_from: Dict[Cell, Optional[Cell]], + start: Cell, exit_cell: Cell) -> List[Cell]: + path = [] + current = exit_cell + while current is not None: + path.append(current) + current = came_from.get(current) + path.reverse() + return path \ No newline at end of file