Kill Process

就是有点类似图的BFS

class Solution(object):
    def killProcess(self, pid, ppid, kill):
        """
        :type pid: List[int]
        :type ppid: List[int]
        :type kill: int
        :rtype: List[int]
        """
        queue = collections.deque([kill])
        store = collections.defaultdict(list)
        for parent, child in zip(ppid, pid):
            store[parent].append(child)

        result = []
        while queue:
            node = queue.pop()
            result.append(node)            
            for child in store[node]:
                queue.appendleft(child)

        return result