python 在递归和非递归模式下的呼吸优先搜索（BFS）算法实现的示例，用于图形扩展和路径查找。

Posted 2021-05-09

#http://eddmann.com/posts/depth-first-search-and-breadth-first-search-in-python/

###CONNECTED COMPONENTS
##NON-RECURSIVE

def bfs(graph, start):
    visited, queue = set(), [start]
    while queue:
        vertex = queue.pop(0)
        if vertex not in visited:
            visited.add(vertex)
            queue.extend(graph[vertex] - visited)
    return visited


###PATH FINDING
##NON-RECURSIVE

def bfs_paths(graph, start, goal):
    queue = [(start, [start])]
    while queue:
        (vertex, path) = queue.pop(0)
        for next in graph[vertex] - set(path):
            if next == goal:
                yield path + [next]
            else:
                queue.append((next, path + [next]))

list(bfs_paths(graph, 'A', 'F')) # [['A', 'C', 'F'], ['A', 'B', 'E', 'F']]

###SHORTEST PATH

def shortest_path(graph, start, goal):
    try:
        return next(bfs_paths(graph, start, goal))
    except StopIteration:
        return None

shortest_path(graph, 'A', 'F') # ['A', 'C', 'F']