8-13、广度优先搜索

1、广度优先搜索，用于图的查找算法，解决两个问题：

从节点A出发，有前往节点B的路径吗？

从节点A出发，前往节点B的哪条路径最短？

graph           = {}
graph["you"]    = ["alice", "bob", "claire"]
graph["bob"]    = ["anuj", "peggy"]
graph["alice"]  = ["peggy"]
graph["claire"] = ["thom", "jonny"]
graph["anuj"]   = []
graph["peggy"]  = []
graph["thom"]   = []
graph["jonny"]  = []

from collections import deque
search_queue =  deque()
search_queue += graph["you"]

def person_is_seller(name):
    return name[-1] == 'm'
	
def search(name):
    search_queue =  deque()
    search_queue += graph[name]
    searched = []
    while search_queue:##只要队列不为空
        person = search_queue.popleft()
        if not person in searched:##仅当这个人没检查过时才检查
            if person_is_seller(person):
                print (person + "is a mango seller!")
                return True
            else :
                search_queue += graph[person]
				search.append(person)##将这个人标记为检查过，否则可能导致无限循环
    return False

search("you")

结果：

找到了最后一个字符为m的人。

1、用散列表可以表示图的链接关系。