排序插入双向链表

Question

I'm trying to make an insertion sort function so that it will sort itself out and then it can display itself in ascending order from top to bottom, and also descending order from bottom to top. It can display sorted from top to bottom ascending, but not descending from bottom to top. Any help?

void DoublyLinkedList::insert(int v){
    Node* p = new Node;
    p->data = v;
    p->next = nullptr;
    p->prev = nullptr;
    if(top == nullptr || top->data > p->data){
        p->next = top;
        top = p;
    }
    else{
        bottom = top;
        while(bottom->next != nullptr && bottom->next->data < p->data){
            bottom = bottom->next;
        }
        bottom->next->prev = p;
        p->next = bottom->next;
        bottom->next = p;
        p->prev = bottom->prev;
        bottom->prev = p;
    }   
    size++
}

Answer 1

There are two possible reasons for the loop to exit; either bottom->next is null or bottom->next->data >= p->data .

The code after the loop assumes that the latter was the reason for exiting, but consider what happen when the item to insert is greater than all the elements in the list.