狄克斯特拉算法

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Date    : 2018-11-30 16:35:01
# @Author  : rorg (928758777)
# @Link    : QQ:928758777
# @Version : $Id$

import os
graph = {}
graph['start'] = {}
graph['start']['a'] = 6
graph['start']['b'] = 2

graph['a'] = {}
graph['a']['c'] = 1
# graph['a']['fin'] = 1
graph['c'] = {}
graph['c']['fin'] = 1

graph['b'] = {}
graph['b']['a'] = 3
graph['b']['fin'] = 5

graph['fin'] = {}


infinity = float('inf')
costs = {}
costs['a'] = 6
costs['b'] = 2
costs['c'] = infinity
costs['fin'] = infinity


parents = {}
parents['a'] = 'start'
parents['b'] = 'start'
parents['c'] = 'a'
parents['fin'] = None

processed = []


def find_lowest_cost_node(costs):
    lowest_cost = float('inf')
    # print("ss", float('inf'))
    lowest_cost_node = None
    for node in costs:
        cost = costs[node]
        if cost < lowest_cost and node not in processed:
            lowest_cost = cost
            lowest_cost_node = node
    return lowest_cost_node


node = find_lowest_cost_node(costs)
# print('nd:', node)
while node is not None:
    cost = costs[node]
    # print('node:', node)
    neighbors = graph[node]
    # print(neighbors)
    for n in neighbors.keys():
        new_cost = cost + neighbors[n]
        if costs[n] > new_cost:
            costs[n] = new_cost
            parents[n] = node
    processed.append(node)
    node = find_lowest_cost_node(costs)

print(costs)
print(processed)