python 图的遍历-深度优先和广度优先

Python的图实现有很多别人已经写好的（比如我下面写的就是参考python-graph），可是不适合一个刚开始的学习的人，我就简化了一下，实现可深度优先和广度优先遍历。

#!/usr/bin/env python

#-*- coding:utf8 -*-

class Graph(object):

def __init__(self, *args, **kwargs):

self.node_neighbors = {}

self.visited = {}

def add_nodes(self, nodelist):

for node in nodelist:

self.add_node(node)

def add_node(self, node):

if not node in self.node_neighbors:

self.node_neighbors[node] = []

def add_edge(self, edge):

u, v = edge

if (v not in self.node_neighbors[u]) and (u not in self.node_neighbors[v]):

self.node_neighbors[u].append(v)

if (u != v):

self.node_neighbors[v].append(u)

def nodes(self):

return self.node_neighbors.keys()

def depth_first_search(self, root=None):

order = []

def dfs(node):

self.visited[node] = True

order.append(node)

for n in self.node_neighbors[node]:

if not n in self.visited:

dfs(n)

if root:

dfs(root)

for node in self.nodes():

if not node in self.visited:

dfs(node)

print order

return order

def breadth_first_search(self, root=None):

queue = []

order = []

def bfs():

while len(queue) > 0:

node = queue.pop(0)

self.visited[node] = True

for n in self.node_neighbors[node]:

if (not n in self.visited) and (not n in queue):

queue.append(n)

order.append(n)

if root:

queue.append(root)

order.append(root)

bfs()

for node in self.nodes():

if not node in self.visited:

queue.append(node)

order.append(node)

bfs()

print order

return order

if __name__ == '__main__':

g = Graph()

g.add_nodes([i+1 for i in range(8)])

g.add_edge((1, 2))

g.add_edge((1, 3))

g.add_edge((2, 4))

g.add_edge((2, 5))

g.add_edge((4, 8))

g.add_edge((5, 8))

g.add_edge((3, 6))

g.add_edge((3, 7))

g.add_edge((6, 7))

print "nodes:", g.nodes()

order = g.depth_first_search(1)

order = g.breadth_first_search(1)



深度优先、广度优先实现比较简单，其他的有权图的关键路径、最短路径等下次实现