// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/use-depth-first-search-in-a-binary-search-tree

var displayTree = (tree) => console.log(JSON.stringify(tree, null, 2));
function Node(value) {
  this.value = value;
  this.left = null;
  this.right = null;
}
function BinarySearchTree() {
  this.root = null;
  // Only change code below this line
  this.inorder = () => {
    if (this.root === null) {
      return null;
    }
    const values = [];
    const traverse = (node) => {
      if (node.left !== null) traverse(node.left);
      values.push(node.value);
      if (node.right !== null) traverse(node.right);
    };
    traverse(this.root);
    return values;
  };

  this.preorder = () => {
    if (this.root === null) {
      return null;
    }
    const values = [];
    const traverse = (node) => {
      values.push(node.value);
      if (node.left !== null) traverse(node.left);
      if (node.right !== null) traverse(node.right);
    };
    traverse(this.root);
    return values;
  };

  this.postorder = () => {
    if (this.root === null) {
      return null;
    }
    const values = [];
    const traverse = (node) => {
      if (node.left !== null) traverse(node.left);
      if (node.right !== null) traverse(node.right);
      values.push(node.value);
    };
    traverse(this.root);
    return values;
  };
  // Only change code above this line
}