This project contains a skeleton for you to implement a binary tree. This is a test-driven project. Run the tests and read the top-most error. If it's not clear what is failing, open the test/test.js file to figure out what the test is expecting. Make the top-most test pass.

Keep making the top-most test pass until all tests pass.

The algorithms for the traversal functions are in the files and are reproduced here.

procedure in order array (node)
  parameter node: a tree node

  if the tree node is null, return an empty array

  // get the array for visiting the left node of node
  // get the array for visiting the right node of node

  // return the left array concatenated with the node value
  //   concatenated with the right array
end procedure in order array

procedure post order array (node)
  parameter node: a tree node

  if the tree node is null, return an empty array

  // get the array for visiting the left node of node
  // get the array for visiting the right node of node

  // return the left array concatenated with the right array
  //   concatenated with the node value
end procedure post order array

• Clone the project from https://github.com/appacademy-starters/data-structures-binary-tree-starter.
• cd into the project folder
• npm install to install dependencies in the project root directory
• npm test to run the specs
• You can view the test cases in test/test.js. Your job is to write code in
  • lib/tree_node.js to implement the TreeNode class
  • lib/tree_order.js to implement the inOrderArray and postOrderArray functions to traverse a tree
  • lib/leet_code_105.js as a scratch pad to work on the LeetCode.com problem at https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/