Binary Tree Traversals

BinaryTree.ts

export class BinaryTreeNode {
  value: number;
  left: BinaryTreeNode | null;
  right: BinaryTreeNode | null;

  constructor(value: number) {
    this.value = value;
    this.left = null;
    this.right = null;
  }
}
export function insertLevelOrder(
  array: number[],
  level: number = 0
): BinaryTreeNode | null {
  let root: BinaryTreeNode | null = null;
  if (level < array.length) {
    root = new BinaryTreeNode(array[level]);
    root.left = insertLevelOrder(array, 2 * level + 1);
    root.right = insertLevelOrder(array, 2 * level + 2);
  }
  return root;
}
export function preOrder(
  root: BinaryTreeNode | null,
  path: number[] = []
): number[] {
  if (!root) {
    return path;
  }
  path.push(root.value);
  if (root.left) {
    preOrder(root.left, path);
  }
  if (root.right) {
    preOrder(root.right, path);
  }
  return path;
}
export function inOrder(
  root: BinaryTreeNode | null,
  path: number[] = []
): number[] {
  if (!root) {
    return path;
  }
  if (root.left) {
    inOrder(root.left, path);
  }
  path.push(root.value);
  if (root.right) {
    inOrder(root.right, path);
  }
  return path;
}
export function postOrder(
  root: BinaryTreeNode | null,
  path: number[] = []
): number[] {
  if (!root) {
    return path;
  }
  if (root.left) {
    postOrder(root.left, path);
  }
  if (root.right) {
    postOrder(root.right, path);
  }
  path.push(root.value);

  return path;
}