1457. Pseudo-Palindromic Paths in a Binary Tree

https://leetcode.com/problems/pseudo-palindromic-paths-in-a-binary-tree

Description

Given a binary tree where node values are digits from 1 to 9. A path in the binary tree is said to be pseudo-palindromic if at least one permutation of the node values in the path is a palindrome.

Return the number of pseudo-palindromic paths going from the root node to leaf nodes.

Example 1:

**Input:** root = [2,3,1,3,1,null,1]
**Output:** 2 
**Explanation:** The figure above represents the given binary tree. There are three paths going from the root node to leaf nodes: the red path [2,3,3], the green path [2,1,1], and the path [2,3,1]. Among these paths only red path and green path are pseudo-palindromic paths since the red path [2,3,3] can be rearranged in [3,2,3] (palindrome) and the green path [2,1,1] can be rearranged in [1,2,1] (palindrome).

Example 2:

**Input:** root = [2,1,1,1,3,null,null,null,null,null,1]
**Output:** 1 
**Explanation:** The figure above represents the given binary tree. There are three paths going from the root node to leaf nodes: the green path [2,1,1], the path [2,1,3,1], and the path [2,1]. Among these paths only the green path is pseudo-palindromic since [2,1,1] can be rearranged in [1,2,1] (palindrome).

Example 3:

**Input:** root = [9]
**Output:** 1

Constraints:

• The number of nodes in the tree is in the range [1, 105].

• 1 <= Node.val <= 9

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