Python BFS广度优先搜索与DFS深度优先搜索

无向图

BFS广度优先搜索

graph = {
    'A': ['B', 'C'],
    'B': ['A', 'C', 'D'],
    'C': ['A', 'B', 'D', 'E'],
    'D': ['B', 'C', 'E', 'F'],
    'E': ['C', 'D'],
    'F': ['D']
}


def BFS(graph, s):
    queue = []
    queue.append(s)
    seen = set()  # seen数组看是否访问过此节点
    seen.add(s)
    while len(queue) > 0:
        vertex = queue.pop(0)
        nodes = graph[vertex]  # graph['A']=['B', 'C']
        for w in nodes:
            if w not in seen:
                queue.append(w)
                seen.add(w)
        print(vertex, end=' ')


BFS(graph, 'A')

输出

A B C D E F 

DFS深度优先搜索

graph = {
    'A': ['B', 'C'],
    'B': ['A', 'C', 'D'],
    'C': ['A', 'B', 'D', 'E'],
    'D': ['B', 'C', 'E', 'F'],
    'E': ['C', 'D'],
    'F': ['D']
}


def BFS(graph, s):
    stack = []
    stack.append(s)
    seen = set()  # seen数组看是否访问过此节点
    seen.add(s)
    while len(stack) > 0:
        vertex = stack.pop()
        nodes = graph[vertex]  # graph['A']=['B', 'C']
        for w in nodes:
            if w not in seen:
                stack.append(w)
                seen.add(w)
        print(vertex, end=' ')


BFS(graph, 'A')

输出

A C E D F B