Leetcode 652 Solution

This article provides solution to leetcode question 652 (find-duplicate-subtrees)
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https://leetcode.com/problems/find-duplicate-subtrees

Solution

# 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 dfs(self, root):
        if root == None:
            return "#"
        res = "{},{},{}".format(
            root.val,
            self.dfs(root.left),
            self.dfs(root.right),
        )

        if res not in self.cache:
            self.cache[res] = root
        else:
            if self.cache[res] is not None:
                self.ans.append(root)
                self.cache[res] = None
        return res

    def findDuplicateSubtrees(self, root):
        """
        :type root: TreeNode
        :rtype: List[TreeNode]
        """
        self.cache = {}
        self.ans = []
        self.dfs(root)
        return self.ans