Python 求二叉树所有左叶节点的和 - V2EX
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woostundy
V2EX    Python

Python 求二叉树所有左叶节点的和

  •  
  •   woostundy 2016-11-11 11:18:37 +08:00 3466 次点击
    这是一个创建于 3264 天前的主题,其中的信息可能已经有所发展或是发生改变。
    python # 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 sumOfLeftLeaves(self, root): """ :type root: TreeNode :rtype: int """ if root is None or self.isleaf(root): return 0 if self.isleaf(root.left): return root.left.val + self.sumOfLeftLeaves(root.right) else: return self.sumOfLeftLeaves(root.left) + self.sumOfLeftLeaves(root.right) def isleaf(self,root): return root.left is None and root.left is None 

    原题地址是 https://leetcode.com/problems/sum-of-left-leaves/ 求解,这段代码哪里写错了?

    7 条回复    2016-11-11 18:40:35 +08:00
    billgreen1
        1
    billgreen1  
       2016-11-11 11:24:14 +08:00
    按我的理解, left leaves != left node

    ~~~python
    def is_leaf(self, node):
    return node is not None and node.left is None and node.right is None
    woostundy
        2
    woostundy  
    OP
       2016-11-11 11:36:06 +08:00
    @billgreen1 是的,求的是所有左叶节点的和。
    node is not None 的判断在最开始就做了。

    错误样例是
    [0,2,4,1,null,3,-1,5,1,null,6,null,8]
    算这个的时候错了
    zmrenwu
        3
    zmrenwu  
       2016-11-11 11:41:05 +08:00
    他不是要你算左叶子节点么?你的代码包含了非叶子节点在里面
    yonka
        4
    yonka  
       2016-11-11 11:52:21 +08:00   1
    return root.left is None and root.left is None

    看了好几遍不知道在干嘛。
    难道不是 return root is not None and root.left is None and root.right is None 吗?
    woostundy
        5
    woostundy  
    OP
       2016-11-11 11:56:04 +08:00
    @yonka 我擦,看出来了,把第二个自判断也写成 left 了。。
    晕,太马虎了
    woostundy
        6
    woostundy  
    OP
       2016-11-11 11:56:31 +08:00
    @billgreen1 是我发现写错了。多谢多谢
    doraemon1293
        7
    doraemon1293  
       2016-11-11 18:40:35 +08:00
    def isleaf(self,root):
    return root.left is None and root.left is None 不应该是 right 吗
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