python數(shù)據(jù)結(jié)構之圖的實現(xiàn)方法

graph = {'A': ['B', 'C'],
 'B': ['C', 'D'],
 'C': ['D'],
 'D': ['C'],
 'E': ['F'],
 'F': ['C']}

def find_path(graph, start, end, path=[]):
 path = path + [start]
 if start == end:
 return path
 if not graph.has_key(start):
 return None
 for node in graph[start]:
 if node not in path:
 newpath = find_path(graph, node, end, path)
 if newpath: return newpath
 return None

def find_all_paths(graph, start, end, path=[]):
 path = path + [start]
 if start == end:
 return [path]
 if not graph.has_key(start):
 return []
 paths = []
 for node in graph[start]:
 if node not in path:
 newpaths = find_all_paths(graph, node, end, path)
 for newpath in newpaths:
 paths.append(newpath)
 return paths

def find_shortest_path(graph, start, end, path=[]):
 path = path + [start]
 if start == end:
 return path
 if not graph.has_key(start):
 return None
 shortest = None
 for node in graph[start]:
 if node not in path:
 newpath = find_shortest_path(graph, node, end, path)
 if newpath:
 if not shortest or len(newpath) < len(shortest):
 shortest = newpath
 return shortest