Grokking Tree Coding Patterns for Interviews
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Pseudo-Palindromic Paths in a Binary Tree (medium)
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Problem Statement

Examples

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Problem Statement

Given a binary tree where each node has a value between 1 and 9, return the number of "pseudo-palindromic" paths from the root node to any leaf node.

A path is called "pseudo-palindromic" if the values along the path can be rearranged to form a palindrome.

Examples

Example 1

  • Input: 
        5
   / \
  4   1
 / \   \
4   1   1
  • Expected Output: 2
  • Justification: The paths are:
    • 5 → 4 → 4 (pseudo-palindromic: "5, 4, 4" can be rearranged to "4, 5, 4")
    • 5 → 1 → 1 (pseudo-palindromic: "5, 1, 1" can be rearranged to "1, 5, 1")

Example 2

  • Input: 
        2
   / \
  3   1
 /   / \
3   1   1
  • Expected Output: 3
  • Justification: All 3 paths are pseudo-palindromic paths.

Example 3

  • Input: 
        9
   / \
  5   5
 /   / \
5   1   7
  • Expected Output: 1
  • Justification: The only path 9 → 5 → 5 is a psuedo-palindromic path.

Constraints:

  • The number of nodes in the tree is in the range [1, 10<sup>5</sup>].
  • 1 <= Node.val <= 9

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Try solving this question here:

Python3
Python3
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On this page

Problem Statement

Examples

Try it yourself