commonAncestor.js

'use strict';

function commonAncestor(n1, n2) {
  var inOrderTra = inOrder(this);
  var postOrderTra = postOrder(this);

  var i1 = inOrderTra.indexOf(n1);
  var i2 = inOrderTra.indexOf(n2);
  var middleNodes = inOrderTra.splice(i1 + 1, i2);

  var map = middleNodes.map(function(i) {
    return {
      i: postOrderTra.indexOf(i)
    };
  });

  // Find the node with the highest index value
  return Object.keys(map).reduce(function(a, b) {
    return map[a] > map[b] ? a : b;
  });
}

/*
Returns an array containing all the elements in the in-order traversal.
@param {BT} root
*/
function inOrder(root) {
  ...
}

/*
Returns an array containing all the elements in the post-order traversal.
@param {BT} root
*/
function postOrder(root) {
  ...
}