maze.py added
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kirill
parent
efd614bd23
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239
svetlakovkyu/02/codes/maze.py
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239
svetlakovkyu/02/codes/maze.py
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import heapq
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import time
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from abc import ABC, abstractmethod
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from collections import deque
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from dataclasses import dataclass, field
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from typing import List, Optional
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class Cell:
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def __init__(self, x, y, is_wall=False, is_start=False, is_exit=False):
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self.x = x
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self.y = y
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self.is_wall = is_wall
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self.is_start = is_start
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self.is_exit = is_exit
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def is_passable(self):
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return not self.is_wall
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def __eq__(self, other):
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return isinstance(other, Cell) and self.x == other.x and self.y == other.y
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def __hash__(self):
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return hash((self.x, self.y))
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def __repr__(self):
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return f"Cell({self.x},{self.y})"
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class Maze:
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def __init__(self, cells, width, height, start, exit_cell):
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self.cells = cells
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self.width = width
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self.height = height
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self.start = start
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self.exit = exit_cell
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def get_cell(self, x, y):
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if 0 <= x < self.width and 0 <= y < self.height:
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return self.cells[y][x]
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return None
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def get_neighbors(self, cell):
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result = []
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for dx, dy in [(0, -1), (0, 1), (-1, 0), (1, 0)]:
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n = self.get_cell(cell.x + dx, cell.y + dy)
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if n and n.is_passable():
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result.append(n)
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return result
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def render(self, path=None):
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path_set = set(path) if path else set()
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lines = []
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for row in self.cells:
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line = ""
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for cell in row:
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if cell.is_start:
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line += " S"
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elif cell.is_exit:
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line += " E"
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elif cell.is_wall:
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line += "##"
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elif cell in path_set:
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line += " ."
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else:
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line += " "
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lines.append(line)
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return "\n".join(lines)
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class MazeBuilder(ABC):
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@abstractmethod
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def build_from_file(self, filename) -> Maze:
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pass
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class TextFileMazeBuilder(MazeBuilder):
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def build_from_file(self, filename) -> Maze:
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with open(filename, encoding="utf-8") as f:
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lines = [l.rstrip("\n") for l in f]
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height = len(lines)
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width = max(len(l) for l in lines)
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cells = []
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start = exit_cell = None
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for y, line in enumerate(lines):
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row = []
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for x in range(width):
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ch = line[x] if x < len(line) else " "
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is_wall = ch == "#"
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is_start = ch == "S"
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is_exit = ch == "E"
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c = Cell(x, y, is_wall, is_start, is_exit)
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if is_start:
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start = c
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if is_exit:
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exit_cell = c
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row.append(c)
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cells.append(row)
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if not start or not exit_cell:
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raise ValueError("Maze must have S and E")
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return Maze(cells, width, height, start, exit_cell)
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@dataclass
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class SearchStats:
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strategy: str
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time_ms: float
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visited: int
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path_length: int
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path: List[Cell] = field(default_factory=list)
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class PathFindingStrategy(ABC):
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_visited = 0
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@property
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def name(self):
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return self.__class__.__name__
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@abstractmethod
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def find_path(self, maze: Maze, start: Cell, end: Cell) -> List[Cell]:
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pass
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@staticmethod
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def _build_path(parent, start, end):
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path, cur = [], end
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while cur:
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path.append(cur)
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cur = parent.get(cur)
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path.reverse()
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return path if path and path[0] == start else []
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class BFSStrategy(PathFindingStrategy):
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@property
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def name(self):
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return "BFS"
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def find_path(self, maze, start, end):
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queue = deque([start])
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parent = {start: None}
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visited = 0
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while queue:
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cur = queue.popleft()
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visited += 1
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if cur == end:
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self._visited = visited
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return self._build_path(parent, start, end)
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for nb in maze.get_neighbors(cur):
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if nb not in parent:
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parent[nb] = cur
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queue.append(nb)
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self._visited = visited
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return []
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class DFSStrategy(PathFindingStrategy):
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@property
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def name(self):
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return "DFS"
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def find_path(self, maze, start, end):
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stack = [start]
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parent = {start: None}
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visited = 0
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while stack:
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cur = stack.pop()
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visited += 1
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if cur == end:
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self._visited = visited
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return self._build_path(parent, start, end)
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for nb in maze.get_neighbors(cur):
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if nb not in parent:
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parent[nb] = cur
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stack.append(nb)
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self._visited = visited
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return []
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class AStarStrategy(PathFindingStrategy):
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@property
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def name(self):
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return "A*"
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@staticmethod
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def _h(a, b):
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return abs(a.x - b.x) + abs(a.y - b.y)
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def find_path(self, maze, start, end):
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counter = 0
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heap = [(0, counter, start)]
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parent = {start: None}
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g = {start: 0}
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closed = set()
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visited = 0
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while heap:
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_, _, cur = heapq.heappop(heap)
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if cur in closed:
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continue
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closed.add(cur)
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visited += 1
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if cur == end:
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self._visited = visited
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return self._build_path(parent, start, end)
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for nb in maze.get_neighbors(cur):
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if nb in closed:
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continue
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ng = g[cur] + 1
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if ng < g.get(nb, float("inf")):
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g[nb] = ng
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counter += 1
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heapq.heappush(heap, (ng + self._h(nb, end), counter, nb))
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parent[nb] = cur
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self._visited = visited
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return []
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class MazeSolver:
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def __init__(self, maze: Maze, strategy: PathFindingStrategy):
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self.maze = maze
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self.strategy = strategy
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def set_strategy(self, strategy: PathFindingStrategy):
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self.strategy = strategy
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def solve(self) -> SearchStats:
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t0 = time.perf_counter()
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path = self.strategy.find_path(self.maze, self.maze.start, self.maze.exit)
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t1 = time.perf_counter()
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return SearchStats(
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strategy=self.strategy.name,
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time_ms=(t1 - t0) * 1000,
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visited=self.strategy._visited,
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path_length=len(path),
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path=path,
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)
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