1
var getDirections = function (root, startValue, destValue) {
2
  const getPath = (node, value, acc = "") => {
3
    if (node === null) {
4
      return "";
5
    } else if (node.val === value) {
6
      return acc;
7
    } else {
8
      return (
9
        getPath(node.left, value, acc + "L") +
10
        getPath(node.right, value, acc + "R")
11
      );
12
    }
13
  };
14

15
  // generate the paths
16
  let startPath = getPath(root, startValue);
17
  let destPath = getPath(root, destValue);
18

19
  // find the lowest common ancestor
20
  let i = 0;
21
  for (
22
    ;
23
    i < startPath.length && i < destPath.length && startPath[i] === destPath[i];
24
    i++
25
  );
26

27
  // output the final path
28
  let output = "";
29
  for (let j = i; j < startPath.length; j++) {
30
    output += "U";
31
  }
32

33
  return output + destPath.substring(i);
34
};