Pseudo-Palindromic Paths in a Binary Tree

Medium

Node values are digits 1-9. A root-to-leaf path is pseudo-palindromic if at least one permutation of its node values is a palindrome. Return the number of pseudo-palindromic root-to-leaf paths.

Example 1

Input:  root = [2,3,1,3,1,null,1]
Output: 2

Example 2

Input:  root = [2,1,1,1,3,null,null,null,null,null,1]
Output: 1

Constraints

• 1 <= number of nodes <= 10^5
• 1 <= Node.val <= 9