Recover swapped BST

A binary search tree had exactly two of its node values swapped by mistake. Given the (possibly corrupted) tree as a level-order array (None marks a missing child), recover it by swapping those two values back, then return the corrected inorder traversal (which must be strictly increasing). Find the two offending nodes during a single inorder walk: the inorder sequence of a BST is sorted, so the swapped pair shows up as one or two descents. Return the corrected inorder list.