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.
//
// 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.
//


/**
 * 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}
 */
var hasPathSum = function(root, sum) {
  if (!root) return false
  if (!root.left && !root.right) {
    return root.val === sum
  }
  return (!!root.left && hasPathSum(root.left, sum-root.val)) ||
    (!!root.right && hasPathSum(root.right, sum-root.val))
};