#1430 - Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree

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Depth-First Search Tree Breadth-First Search Binary Tree

Problem Description

Given a binary tree where each path going from the root to any leaf form a valid sequence, check if a given string is a valid sequence in such binary tree.

We get the given string from the concatenation of an array of integers arr and the concatenation of all values of the nodes along a path results in a sequence in the given binary tree.

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
 * @param {number[]} arr
 * @return {boolean}
 */
var isValidSequence = function(root, arr) {
  return dfs(root, 0);

  function dfs(node, index) {
    if (!node || index >= arr.length || node.val !== arr[index]) {
      return false;
    }

    if (index === arr.length - 1) {
      return !node.left && !node.right;
    }

    return dfs(node.left, index + 1) || dfs(node.right, index + 1);
  }
};