103 lines
3.7 KiB
Python
103 lines
3.7 KiB
Python
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def parse_grid(file_path):
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"""Parses the grid from a file and returns it as a 2D list."""
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try:
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with open(file_path, 'r') as file:
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grid = [list(line.strip()) for line in file]
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print(f"Grid parsed from {file_path}:")
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[print(''.join(row)) for row in grid]
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return grid
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except Exception as e:
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print(f"Error reading file {file_path}: {e}")
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raise
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def create_graph(grid):
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"""Creates a graph from the grid."""
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graph = {}
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rows, cols = len(grid), len(grid[0])
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for r in range(rows):
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for c in range(cols):
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if grid[r][c] in "|-LJ7FS":
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graph[(r, c)] = get_neighbors(grid, r, c)
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print("Graph created from grid:")
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print(graph)
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return graph
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def get_neighbors(grid, r, c):
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"""Finds the neighbors of a cell in the grid."""
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neighbors = []
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rows, cols = len(grid), len(grid[0])
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# Directions: North, East, South, West
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directions = [(r-1, c), (r, c+1), (r+1, c), (r, c-1)]
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connected = {
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"|": [0, 2], "-": [1, 3],
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"L": [0, 1], "J": [0, 3],
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"7": [2, 3], "F": [1, 2],
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"S": [0, 1, 2, 3] # 'S' connects in all directions for initial identification
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}
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for i, (dr, dc) in enumerate(directions):
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if 0 <= dr < rows and 0 <= dc < cols and grid[dr][dc] != '.':
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neighbor_type = grid[dr][dc]
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# Check if there is a valid connection
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if neighbor_type in connected:
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if i in connected[grid[r][c]] and (3-i) in connected[neighbor_type]: # Check reverse direction
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neighbors.append((dr, dc))
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print(f"Neighbors for ({r}, {c}): {neighbors}")
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return neighbors
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def bfs(graph, start):
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"""Performs BFS on the graph and returns the maximum distance from the start."""
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visited = set()
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queue = [(start, 0)]
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max_distance = 0
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while queue:
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node, distance = queue.pop(0)
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if node != start or len(visited) == 0: # Allow revisiting start only initially
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visited.add(node)
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max_distance = max(max_distance, distance)
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print(f"Visited node: {node}, Distance: {distance}")
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for neighbor in graph[node]:
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if neighbor not in visited or (neighbor == start and len(visited) > 1):
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queue.append((neighbor, distance + 1))
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print(f"Maximum distance from start: {max_distance}")
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return max_distance
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def find_start(grid):
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"""Finds the starting position 'S' in the grid."""
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for r, row in enumerate(grid):
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for c, cell in enumerate(row):
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if cell == 'S':
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print(f"Starting position found at: ({r}, {c})")
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return r, c
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raise ValueError("Starting position 'S' not found in the grid")
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def run_test(file_path):
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"""Runs the algorithm on a test file and asserts the result."""
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print(f"Running test with file: {file_path}")
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grid = parse_grid(file_path)
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graph = create_graph(grid)
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start = find_start(grid)
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max_distance = bfs(graph, start)
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print(f"Max distance for test: {max_distance}")
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return max_distance
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def main(file_path):
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"""Main function to run the algorithm on the input file."""
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print(f"Running main algorithm with file: {file_path}")
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grid = parse_grid(file_path)
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graph = create_graph(grid)
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start = find_start(grid)
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max_distance = bfs(graph, start)
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print(f"Max distance for input: {max_distance}")
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return max_distance
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if __name__ == "__main__":
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test_result = run_test("../test.txt")
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assert test_result == 8, f"Test failed: expected 8, got {test_result}"
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print(f"Test passed with {test_result}")
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input_result = main("../input.txt")
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print(f"Result for input file: {input_result}")
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