python实现Dijkstra算法

下面是用python实现Dijkstra算法的代码：

# -*- coding: utf-8 -*-
"""
Created on Fri Jul 07 11:33:19 2017

@author: linzr
"""
## 表示无穷大
INF_val = 9999

class Dijkstra_Path():
def __init__(self, node_map):
self.node_map = node_map
self.node_length = len(node_map)
self.used_node_list = []
self.collected_node_dict = {}

def __call__(self, from_node, to_node):
self.from_node = from_node
self.to_node = to_node
self._init_dijkstra()
return self._format_path()

def _init_dijkstra(self):
## Add from_node to used_node_list
self.used_node_list.append(self.from_node)
for index1 in range(self.node_length):
self.collected_node_dict[index1] = [INF_val, -1]

self.collected_node_dict[self.from_node] = [0, -1] # from_node don't have pre_node
for index1, weight_val in enumerate(self.node_map[self.from_node]):
if weight_val:
self.collected_node_dict[index1] = [weight_val, self.from_node] # [weight_val, pre_node]

self._foreach_dijkstra()

def _foreach_dijkstra(self):
while(len(self.used_node_list) < self.node_length - 1):
min_key = -1
min_val = INF_val
for key, val in self.collected_node_dict.items(): # 遍历已有权值节点
if val[0] < min_val and key not in self.used_node_list:
min_key = key
min_val = val[0]

## 把最小的值加入到used_node_list
if min_key != -1:
self.used_node_list.append(min_key)

for index1, weight_val in enumerate(self.node_map[min_key]):
## 对刚加入到used_node_list中的节点的相邻点进行遍历比较
if weight_val > 0 and self.collected_node_dict[index1][0] > weight_val + min_val:
self.collected_node_dict[index1][0] = weight_val + min_val # update weight_val
self.collected_node_dict[index1][1] = min_key

def _format_path(self):
node_list = []
temp_node = self.to_node
node_list.append((temp_node, self.collected_node_dict[temp_node][0]))
while self.collected_node_dict[temp_node][1] != -1:
temp_node = self.collected_node_dict[temp_node][1]
node_list.append((temp_node, self.collected_node_dict[temp_node][0]))
node_list.reverse()
return node_list

def set_node_map(node_map, node, node_list):
for x, y, val in node_list:
node_map[node.index(x)][node.index(y)] = node_map[node.index(y)][node.index(x)] = val

if __name__ == "__main__":
node = ['A', 'B', 'C', 'D', 'E', 'F', 'G']
node_list = [('A', 'F', 9), ('A', 'B', 10), ('A', 'G', 15), ('B', 'F', 2),
('G', 'F', 3), ('G', 'E', 12), ('G', 'C', 10), ('C', 'E', 1),
('E', 'D', 7)]

## init node_map to 0
node_map = [[0 for val in xrange(len(node))] for val in xrange(len(node))]

## set node_map
set_node_map(node_map, node, node_list)

## select one node to obj node, e.g. A --> D(node[0] --> node[3])
from_node = node.index('A')
to_node = node.index('E')
dijkstrapath = Dijkstra_Path(node_map)
path = dijkstrapath(from_node, to_node)
print path
网络拓扑图如下：



运行结果为[(0, 0), (5, 9), (6, 12), (2, 22), (4, 23)]