Python-廣度優先搜索

如圖所示：

 

以此圖爲例尋找末尾爲「m」的名稱。這裏使用廣度優先搜索，這個能夠回答兩類問題：

第一類問題：從節點A出發，有前往節點B的路徑嗎？

第二類問題：從節點A出發，前往節點B的哪條路徑最短？

那這裏其實就是尋找末尾爲「m」名稱的最短路徑。

from collections import deque


def person_is_seller(name):
    return name[-1] == 'm'

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"] = []

def search(name):
    search_queue = deque()
    search_queue += graph[name]
    searched = []
    while search_queue:
        person = search_queue.popleft()
        if person not in searched:
            if person_is_seller(person):
                print(person + ' is a mongo seller')
                return True
            else:
                search_queue += graph[person]
                searched.append(person)
    return False

search("you")

這裏使用到了散列表的概念，以及Python中deque函數來建立一個雙端隊列。