Maximum Tree Path Sum

Given a binary tree, find the path with the maximum path sum. The path must contain at least one node and does not necessarily need to go through the root. Input Format The tree's nodes are represented by integers, including both positive and negative numbers. Output Format Return the maximum path sum. Test Cases Input: [-10,9,20,null,null,15,7] Output: 42 Input: [-3] Output: -3 Input: [1,2,3] Output: 6 Input: [2,-1] Output: 2 Input: [5,-6,-7] Output: 5 Example Input -10,9,20,null,null,15,7