559. N叉树的最大深度

方法一：BFS模板的应用。

总结的DFS、BFS模板参考：https://www.cnblogs.com/panweiwei/p/13065661.html

class Solution(object):
    def maxDepth(self, root):
        """
        :type root: Node
        :rtype: int
        """
        if not root:
            return 0
        if not root.children:
            return 1
        res = 0
        stack = [root]
        while stack:
            sizeStack = len(stack)
            for i in range(sizeStack):
                node = stack.pop(0)
                for item in node.children:
                    if item:
                        stack.append(item)
            res += 1
        return res

方法二：DFS模板的应用。

class Solution(object):
    def maxDepth(self, root):
        """
        :type root: Node
        :rtype: int
        """
        if not root:
            return 0
        if not root.children:
            return 1
        return max(1+self.maxDepth(child) for child in root.children)