Morris Binary Tree Traversal [space - O(1)]

Problem Statement Given the root of a binary tree, return the inorder traversal of its nodes' values. (link) Example 1: Input: root = [1,null,2,3] Output: [1,3,2] Explanation: Example 2: Input: root = [1,2,3,4,5,null,8,null,null,6,7,9] Output: [4,2,...