leetcode332

没能做出来，参考别人的：

from heapq import heapify, heappush, heappop

class Solution:
    def findItinerary(self, tickets: List[List[str]]) -> List[str]:
        graph = collections.defaultdict(list)
        for src, des in tickets:
            heappush(graph[src], des)
        res = []
        self.DFS('JFK', graph, res)
        return res[::-1]

    def DFS(self, src, graph, res):
        while graph[src]:
            self.DFS(heappop(graph[src]), graph, res)
        res += [src]
        return

参考地址：https://leetcode.com/problems/reconstruct-itinerary/discuss/489268/Clean-Python-solution-beats-99-in-time-100-in-space

算法思路：深度优先遍历DFS + 堆。在中等难度的题目中，这道题目属于比较困难的了。