LeetCode Binary Tree Level Order Traversal II

LeetCode解题之Binary Tree Level Order Traversal II

原题

实现树的广度优先遍历的倒序遍历，即从最底层依次向上遍历，每一层上的数据按照从左到右的顺序排列。

注意点：

• 无

例子:

输入:

    3
   / \   9  20
    /  \    15   7

输出:

[
  [15,7],
  [9,20],
  [3]
]

解题思路

直接复用了 Binary Tree Level Order Traversal 的代码，只是最后把序列翻转了。

AC源码

# Definition for a binary tree node.
class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None


class Solution(object):
    def levelOrderBottom(self, root):
        """ :type root: TreeNode :rtype: List[List[int]] """
        result = []
        if not root:
            return result
        curr_level = [root]
        while curr_level:
            level_result = []
            next_level = []
            for temp in curr_level:
                level_result.append(temp.val)
                if temp.left:
                    next_level.append(temp.left)
                if temp.right:
                    next_level.append(temp.right)
            result.append(level_result)
            curr_level = next_level
        result.reverse()
        return result


if __name__ == "__main__":
    None

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