Leetcode

Given a binary tree, return the inorder traversal of its nodes' values. Example: Input: [1,null,2,3] 1 \ 2 / 3 Output: [1,3,2] Solution 1: Recursion Recursion is the go-to method when dealing with tree data structures. In this problem, the tree needs to be printed out as inorder, which means to put root node in between left subtree and right subtree. Therefore, the recursion solution is done by recursively calling a funtion with a tree node as the argument.