Python describe LeetCode 508. The most frequent sub tree elements and

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subject

Give you a root node of binary tree root , Please return the most frequent subtree elements and . If more than one element appears the same number of times , Returns all the most frequent subtree elements and （ Unlimited order ）.

Of a node 「 Subtree elements and 」 It is defined as the sum of the elements of all nodes in the binary tree with the node as the root （ Including the node itself ）.

Example 1：

 Input : root = [5,2,-3]
Output : [2,-3,4]

Example 2：

 Input : root = [5,2,-5]
Output : [2]

Tips :

• The number of nodes is [1, 104] Within the scope of
• -105 <= Node.val <= 105

Python describe

Recursive computation sum, Count the number of occurrences

# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def findFrequentTreeSum(self, root: TreeNode) -> List[int]:
tmp = {
}
def get_sum(node):
if node is None:
return 0
s = get_sum(node.left) + get_sum(node.right) + node.val
tmp[s] = tmp.get(s,[]) + [node.val,]
return s
get_sum(root)
max_len = 0
for item in tmp.values():
max_len = max(max_len,len(item))
res = []
for key,item in tmp.items():
if len(item) == max_len:
res.append(key)
return res