二叉树打印

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按层打印二叉树

任务描述：有一课二叉树，设计一个算法，按照层次打印这棵二叉树。给定二叉树的根节点root，返回打印结果数组，结果按照每一层一个数组进行储存，数组排列顺序按照从上到下，数组内元素顺序按从左往右。

Python实现

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# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None


class TreePrinter:
    def printTree(self, root):
        # write code here
        if root is None:
            return []
        else:
            queue = [root, "#"]
            res = []
            temp = []
            while queue:
                cur = queue.pop(0)
                if cur == "#":
                    res.append(temp)
                    temp = []
                else:
                    temp.append(cur.val)
                    if cur.left:
                        queue.append(cur.left)
                    if cur.right:
                        queue.append(cur.right)
                    if queue[0] == "#":
                        queue.append("#")
            return res[:-1]