404. Sum of Left Leaves

Easy

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Share Find the sum of all left leaves in a given binary tree.

Example:

3复制代码

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There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

思路：深度搜索算法，是左子树，且没有子节点，add

代码：python3

class Solution(object):    def sumOfLeftLeaves(self, root):        cache=[0]        def dfs(root,left):            if not root:return            if left and not root.left and not root.right:                cache[0] += root.val            dfs(root.left,True)            dfs(root.right,False)        dfs(root,False)        return cache[0]复制代码