python实现Floyd算法

原文链接：http://blog.csdn.net/u011285477/article/details/75096303【侵删】

下面是用Python实现Floyd算法的代码：

# -*- coding: utf-8 -*-  
""" 
Created on Thu Jul 13 14:56:37 2017 
 
@author: linzr 
"""  
  
## 表示无穷大  
INF_val = 9999  
  
class Floyd_Path():  
    def __init__(self, node, node_map, path_map):  
        self.node = node  
        self.node_map = node_map  
        self.node_length = len(node_map)  
        self.path_map = path_map  
        self._init_Floyd()  
      
    def __call__(self, from_node, to_node):  
        self.from_node = from_node  
        self.to_node = to_node  
        return self._format_path()  
  
    def _init_Floyd(self):  
        for k in range(self.node_length):  
            for i in range(self.node_length):  
                for j in range(self.node_length):  
                    tmp = self.node_map[i][k] + self.node_map[k][j]  
                    if self.node_map[i][j] > tmp:  
                        self.node_map[i][j] = tmp  
                        self.path_map[i][j] = self.path_map[i][k]  
                          
        print '_init_Floyd is end'  
  
  
    def _format_path(self):  
        node_list = []  
        temp_node = self.from_node  
        obj_node = self.to_node  
        print("the shortest path is: %d")%(self.node_map[temp_node][obj_node])  
        node_list.append(self.node[temp_node])  
        while True:  
            node_list.append(self.node[self.path_map[temp_node][obj_node]])  
            temp_node = self.path_map[temp_node][obj_node]  
            if temp_node == obj_node:  
                break;  
          
        return node_list  
                  
  
          
  
  
def set_node_map(node_map, node, node_list, path_map):  
    for i in range(len(node)):  
        ## 对角线为0  
        node_map[i][i] = 0  
    for x, y, val in node_list:  
        node_map[node.index(x)][node.index(y)] = node_map[node.index(y)][node.index(x)] = val  
        path_map[node.index(x)][node.index(y)] = node.index(y)  
        path_map[node.index(y)][node.index(x)] = node.index(x)  
  
      
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)]  
    
    ## node_map[i][j] 存储i到j的最短距离  
    node_map = [[INF_val for val in xrange(len(node))] for val in xrange(len(node))]  
    ## path_map[i][j]=j 表示i到j的最短路径是经过顶点j  
    path_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, path_map)  
  
   
    ## select one node to obj node, e.g. A --> D(node[0] --> node[3])  
    from_node = node.index('A')  
    to_node = node.index('E')  
    Floydpath = Floyd_Path(node, node_map, path_map)  
    path = Floydpath(from_node, to_node)  
    print path

 网络拓扑图如下：

运行结果为： the shortest path is: 23
['A', 'F', 'G', 'C', 'E']