Path Sum

Description

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

Note: A leaf is a node with no children.

Example:

Given the below binary tree and sum = 22,

      5
     / \
    4   8
   /   / \
  11  13  4
 /  \      \
7    2      1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

Solution(javascript)

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} sum
 * @return {boolean}
 */
const hasPathSum = (root, sum) => {
  const aux = (node, currentSum) => {
    if (!node) {
      return false
    }
    if (node && !node.left && !node.right) {
      return (currentSum + node.val) === sum
    }
    const isLeftHas = aux(node.left, currentSum + node.val)
    const isRightHas = aux(node.right, currentSum + node.val)
    return (isLeftHas || isRightHas)
  }
  if (root === null) {
    return false
  }
  return aux(root, 0)
}