#1457 - Pseudo-Palindromic Paths in a Binary Tree

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Depth-First Search Tree Breadth-First Search Bit Manipulation Binary Tree

Problem 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.

Solution

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var pseudoPalindromicPaths = function(root) {
  const frequency = new Array(10).fill(0);
  let count = 0;

  traverse(root);

  return count;

  function traverse(node) {
    if (!node) return;

    frequency[node.val]++;

    if (!node.left && !node.right) {
      let oddCount = 0;
      for (let i = 1; i <= 9; i++) {
        if (frequency[i] % 2 !== 0) oddCount++;
      }
      if (oddCount <= 1) count++;
    }

    traverse(node.left);
    traverse(node.right);

    frequency[node.val]--;
  }
};