题解 | 按之字形顺序打印二叉树

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param pRoot TreeNode类 
# @return int整型二维数组
#
class Solution:
    def Print(self , pRoot: TreeNode) -> List[List[int]]:
        # write code here
        if not pRoot:
            return []
        node = pRoot
        num = []
        ls = [node]
        k = 1
        while ls:
            row = []
            next_level = []
            if k % 2 == 1:
                for n in range(len(ls)):
                    node = ls.pop()
                    row.append(node.val)
                    if node.left:
                        next_level.append(node.left)
                    if node.right:
                        next_level.append(node.right)
                num.append(row)
                ls = next_level
                k += 1
            elif k % 2 == 0:
                for n in range(len(ls)):
                    node = ls.pop()
                    row.append(node.val)
                    if node.right:
                        next_level.append(node.right)
                    if node.left:
                        next_level.append(node.left)
                num.append(row)
                ls = next_level
                k += 1 
        return num