LeetCode Binary Tree Level Order Traversal II

LeetCode解題之Binary Tree Level Order Traversal II

原題

實作樹的廣度優先周遊的倒序周遊，即從最底層依次向上周遊，每一層上的資料按照從左到右的順序排列。

注意點：

• 無

例子:

輸入:

3
   / \
  9  20
    /  \
   15   7
           

輸出:

[
  [,],
  [,],
  []
]
           

解題思路

直接複用了 Binary Tree Level Order Traversal 的代碼，隻是最後把序列翻轉了。

AC源碼

# 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
           

歡迎檢視我的Github (https://github.com/gavinfish/LeetCode-Python) 來獲得相關源碼。