Assign product to the last level category in magento 2

Question

we are importing product from outside of magento.we create an mappings for all attributes as target attributes and magento attributes.we have categorys as Abc/Cde/efg.Here is my category mapping code

                  foreach($Categories as $Category)
                     {
                        $categories = explode('/', $Category);

                        if(count($categories) > 0)
                        {
                            $level = 2;
                            $parentId = 2;
                            foreach($categories as $category) {
                                $categoryCollection = $categoryModel->getCollection();
                                $categoryCollection->addAttributeToFilter('name', array('eq' => $category));
                                $categoryCollection->addFieldToFilter('level', array('eq' => $level));
                                $categoryCollection->addFieldToFilter('parent_id', array('eq' => $parentId));


                                if($categoryCollection->getSize() > 0)
                                {
                                    $return[$mapping->getAttribute()][] = $parentId = $categoryCollection->getFirstItem()->getId();
                                }

                                $level++;
                            }

                        }

                    }

i will loop into categories and assign it level wise. Now i need to change the code as i need to assign to the last category only i.e abc/cde/fdf categorys are there i need to assign only to fdf category only.how can i change my code to assign to last category only.