python实现图的遍历（递归和非递归）

class graph:

    def __init__(self,value):

        self.value=value

        self.neighbors=None

# 图的广度优先遍历

# 1.利用队列实现

# 2.从源节点开始依次按照宽度进队列，然后弹出

# 3.每弹出一个节点，就把该节点所有没有进过队列的邻接点放入队列

# 4.直到队列变空

from queue import Queue

def bfs(node):

    if node is None:

        return

    queue = Queue()

    nodeSet = set()

    queue.put(node)

    nodeSet.add(node)

    while not queue.empty():

        cur = queue.get()               # 弹出元素

        print(cur.value)                # 打印元素值

        for next in cur.neighbors:          # 遍历元素的邻接节点

            if next not in nodeSet:     # 若邻接节点没有入过队，加入队列并登记

                nodeSet.add(next)

                queue.put(next)

# 图的深度优先遍历(非递归)

# 1.利用栈实现

# 2.从源节点开始把节点按照深度放入栈，然后弹出

# 3.每弹出一个点，把该节点下一个没有进过栈的邻接点放入栈

# 4.直到栈变空

def dfs(node):

    if node is None:

        return

    nodeSet = set()

    stack = []

    print(node.value)

    nodeSet.add(node)

    stack.append(node)

    while len(stack) > 0:

        cur = stack.pop()               # 弹出最近入栈的节点

        for next in cur.neighbors:         # 遍历该节点的邻接节点

            if next not in nodeSet:    # 如果邻接节点不重复

                stack.append(cur)       # 把节点压入

                stack.append(next)      # 把邻接节点压入

                nodeSet.add(next)           # 登记节点

                print(next.value)       # 打印节点值

                break                   # 退出，保持深度优先

def dfs1(node,nodeset):#递归深度优先遍历

    if node is None:

        return

    print(node.value)

    nodeset.add(node)

    for next in node.neighbors:

        if next not in nodeset:

            dfs1(next, nodeset)

node5=graph(5)

node4=graph(4)

node3=graph(3)

node2=graph(2)

node1=graph(1)

nodeset=set()

node4.neighbors=[node3,node2,node1]

node3.neighbors=[node4]

node2.neighbors=[node4,node5]

node1.neighbors=[node4]

node5.neighbors=[node2]

dfs1(node4,nodeset)

dfs(node4)

bfs(node4)