FixingTwoNodesInABST

class GfG
{
    Node first, second, last, prev;
    void inorder(Node root)
    {
        if(root == null)
            return;
        inorder(root.left);
        
        if(prev != null && root.data < prev.data)
        {
            if(first != null)
                last = root;
            else
            {
                first = prev;
                second = root;
            }
        }
        prev = root;
        inorder(root.right);
        
    }
    public Node correctBST(Node root)
    {
        prev = first = second = last = null;
        inorder(root);
        
        if(last == null)
        {
            int temp = first.data;
            first.data = second.data;
            second.data = temp;
        }
        else
        {
            int temp = first.data;
            first.data = last.data;
            last.data = temp;
        }
        return root;
    }
    
}