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#ifndef SINGLY_LINKED_LIST_HPP
#define SINGLY_LINKED_LIST_HPP
struct ListNode
{
int _data{ 0 };
ListNode* _next{ nullptr };
};
struct SinglyLinkedList
{
size_t _size{ 0 };
ListNode* _head{ nullptr };
};
bool Append(SinglyLinkedList* list, ListNode* node);
bool Prepend(SinglyLinkedList* list, ListNode* node);
bool RemoveFirst(SinglyLinkedList* list);
bool RemoveLast(SinglyLinkedList* list);
bool InsertAfter(SinglyLinkedList* list, const int data, ListNode* node);
bool InsertBefore(SinglyLinkedList* list, const int data, ListNode* node);
bool Clear(SinglyLinkedList* list);
ListNode* Extract(SinglyLinkedList* list, const int data);
bool Empty(SinglyLinkedList* list);
bool Remove(SinglyLinkedList* list, ListNode* node);
//code
bool Append(SinglyLinkedList* list, ListNode* node )
{
//we have a list
//we need to add a node to the end of the list
//empty
if (Empty(list))
{
list->_head = node;
list->_size++;
return true;
}
//Append head
if(list->_size == 1)
{
list->_head->_next = node;
list->_size++;
return true;
}
//Down the list
ListNode* travel = nullptr;
for(travel = list->_head; travel->_next != nullptr;)
{
travel = travel->_next;
}
travel->_next = node;
list->_size++;
return true;
}
bool Prepend(SinglyLinkedList* list, ListNode* node)
{
if (Empty(list))
{
list->_head = node;
list->_size++;
return true;
}
node->_next = list->_head;
list->_head = node;
list->_size++;
return true;
}
bool RemoveFirst(SinglyLinkedList* list)
{
//check if zero size
if (Empty(list)) return true;
if(list->_size == 1)
{
list->_head = nullptr;
}
else
{
ListNode* prev = list->_head;
list->_head = list->_head->_next;
prev->_next = nullptr;
}
list->_size--;
return true;
}
bool RemoveLast(SinglyLinkedList* list)
{
if (Empty(list)) return true;
if (list->_size == 1)
{
list->_head = nullptr;
return true;
}
ListNode* travel = list->_head;
while(travel->_next->_next != nullptr)
{
travel = travel->_next;
}
travel->_next = nullptr;
list->_size--;
return true;
}
bool InsertAfter(SinglyLinkedList* list, const int data, ListNode* node)
{
//first to find data
//thoughts? What if we are inserting at after end.
ListNode* travel;
for (travel = list->_head; travel->_data != data && travel->_next != nullptr; )
{
travel = travel->_next;
}
if (travel->_next == nullptr)
{
return Append(list, node);
}
node->_next = travel->_next;
travel->_next = node;
list->_size++;
//then insert after data
return true;
}
bool InsertBefore(SinglyLinkedList* list, const int data, ListNode* node)
{
if (list->_head->_data == data)
return Prepend(list, node);
ListNode* travel;
for (travel = list->_head; travel->_next->_data != data;)
{
travel = travel->_next;
}
node->_next = travel->_next;
travel->_next = node;
list->_size++;
return true;
}
bool Clear(SinglyLinkedList* list)
{
//consider the head
//consider the size
//We have to detach every node from each other
//start at the head
//use a node* to track our position
if (list->_size == 0) return true;
ListNode* travel = list->_head;
ListNode* prev = travel;
do
{
prev = travel;
travel = travel->_next;
prev->_data = 0;
prev->_next = nullptr;
} while (travel != nullptr && travel->_next != nullptr);
list->_size = 0;
list->_head = nullptr;
return true;
}
ListNode* Extract(SinglyLinkedList* list, const int data)
{
//check if empty, shortcut return
ListNode* temp = new ListNode{0, nullptr};
ListNode* travel = nullptr;
if (Empty(list))
{
return temp;
}
//Read through list
for (travel = list->_head; travel->_data != data && travel->_next != nullptr; )
{
travel = travel->_next;
}
//find the data
//pointer to the node
temp->_data = travel->_data;
//remove node from list
if(Remove(list, travel))
{
return temp;
}
//or don't find data
return nullptr;
}
bool Remove(SinglyLinkedList* list, ListNode* node)
{
//find the node
//Read through list
ListNode* travel = list->_head;
ListNode* prev = travel;
while(travel != node)
{
prev = travel;
travel = travel->_next;
}
//if first, remove first
if(travel == list->_head)
{
return RemoveFirst(list);
}
//if last, remove last
if(travel->_next == nullptr)
{
return RemoveLast(list);
}
//else in middle
//remove travel's node
//will need previous node
//to set previous's next to travel's next
prev->_next = travel->_next; //fixing pointer between nodes
//removes dangling pointer from prev to travel
//delete travel
travel->_next = nullptr;
travel->_data = 0;
list->_size--;
}
bool Empty(SinglyLinkedList* list)
{
return (list->_size == 0 && list->_head == nullptr);
}
#endif // !SINGLY_LINKED_LIST_HPP
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