LintCode:二叉树的锯齿形层次遍历

LintCode:二叉树的锯齿形层次遍历

"""
Definition of TreeNode:
class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left, self.right = None, None
"""


class Solution:
    """
    @param root: The root of binary tree.
    @return: A list of list of integer include 
             the zig zag level order traversal of its nodes' values
    """
    def zigzagLevelOrder(self, root):
        # write your code here
        if root == None:
            return []
        L1 = [root]
        ans = [[root.val]]
        flag = 1
        while L1:
            L2 = []
            L3 = []
            while L1:
                node = L1[0]
                if node.left != None:
                    L2.append(node.left)
                if node.right != None:
                    L2.append(node.right)
                L1.remove(node)
            if L2:
                if flag % 2 == 1:
                    L3 = [node.val for node in L2][::-1]
                else:
                    L3 = [node.val for node in L2]
                flag += 1
                ans.append(L3)
            L1 = L2
        return ans