path-sum.js

/**
 * 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.
 *
 * For 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.
 */

/**
 * @param {TreeNode} root
 * @param {number} sum
 * @return {boolean}
 */
const hasPathSum = (root, sum) => {
  if (!root) {
    return false;
  }

  if (!root.left && !root.right) {
    return root.val === sum;
  }

  return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
};

export default hasPathSum;