LeetCode: [103] 二叉树的锯齿形层序遍历

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# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    
    def zigzagLevelOrder(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        res = []
        if root is None:
            return res
        if root.left is None and root.right is None:
            res.append([root.val])
            return res

        height = self.height(root)
        nodelist = [root]
        for i in range(0, height):
            subnodelist = []
            subres = []
            while nodelist:
                cur = nodelist.pop(0)
                subres.append(cur.val)
                if cur.left:
                    subnodelist.append(cur.left)
                if cur.right:
                    subnodelist.append(cur.right)

            nodelist = subnodelist
            if i % 2 != 0:
                subres.reverse()
            res.append(subres)

        return res

    def height(self, tree):
        if tree is None:
            return 0
        else:
            return 1 + max(self.height(tree.left), self.height(tree.right))