give binary tree root return maximum sum key subtree Binary Search Tree bstassume BST define followsthe leave subtree node contain node key node keythe right subtree node contain nod key great node keyBoth leave right subtree binary search tree Example 1input root 1432425nullnullnullnullnullnull46output 20explanation maximum sum valid Binary search tree obtain root node key equal 3example 2input root 43null12output 2explanation maximum sum valid Binary search tree obtain single root node key equal 2example 3input root 425output 0explanation all value negative return BST ConstraintsThe number nod tree range 1 4 1044 104 Nodeval 4 104