Data.Structures.For.Game.Programmers.PART2.Basics.6.LinkedLists

1.Linked List
  Each node in a linked list points to the next node in the list.

2.Singly Linked Lists
  Each node in the list points only to the next node.

3.The SListNode Class
  two data members: m_data and m_next;
[Data]

template <class Datatype>class SListNode{public:Datatype m_data;SListNode<Datatype>* m_next;};

  create a list:

SListNode<int>* list = new SListNode<int>;list->m_data = 10;list->m_next = new SListNode<int>;list->m_next->m_data = 20;

[InsertAfter Func]insert a node after the current node
  This process has two steps:
1.Create a new node that points to the one after the current node.
2.Make the one before the current node point to  the new node.

void InsertAfter(Datatype p_data){SListNode<Datatype>* newnode = new SListNode<Datatype>;newnode->m_data = p_data;newnode->m_next = m_next;m_next = newnode;}

4.Iterators // 游标,迭代器
  You need to have some way of moving through a linked list and accessing all of the nodes.
  An iterator is simply a structure that allows you to move through a linked list from start to finish.An iterator basically points to a specific node in a list.

5.A linked list
  I preferred to wrap the node structure into another class.

template <class Datatype>class SLinkedList{public:SListNode<Datatype>* m_head;SListNode<Datatype>* m_tail;int m_count;};

[Cons & Des]

SLinkedList(){m_head = 0;m_tail = 0;m_count = 0;}~SLinkedList(){SListNode<Datatype>* itr = m_head;SListNode<Datatype>* next;while (itr != 0){next = itr->m_next;delete itr;itr = next;}}

[Append Func]

void Append(Datatype p_data){if (m_head == 0){m_head = m_tail = new SListNode<Datatype>;m_head->m_data = p_data;}else{m_tail->InsertAfter(p_data);m_tail = m_tail->m_next;}m_count ++;}

[Prepend Func] add items to the beginning

void Prepend(Datatype p_data){SListNode<Datatype>* newnode = new SListNode<Datatype>;newnode->m_data = p_data;newnode->m_next = m_head;m_head = newnode;if (m_tail == 0) m_tail = m_head;m_count ++;}

[RemoveHead Func] remove nodes from the beginning of a list

void RemoveHead(){SListNode<Datatype>* node = 0;if (m_head != 0){node = m_head->m_next;delete m_head;m_head = node;if (m_head == 0)m_tail = 0;m_count --;}}

[RemoveTail]

void RemoveTail(){SListNode<Datatype>* node = m_head;if (m_head != 0){if (m_head == m_tail){delete m_head;m_head = m_tail = 0;}else{while (node->m_next != m_tail)node = node->m_next;m_tail = node;delete node->m_next;node->m_next = 0;}m_count --;}}

6.SListIterator Class
  It contains two things: A pointer to the current node and a pointer to the list the node is in.
[Data]

template <class Datatype>class SListIterator{public:SListNode<Datatype>* m_node;SLinkedList<Datatype>* m_list;};

[Cons]

SListIterator(SLinkedList<Datatype>* p_list = 0, SListNode<Datatype>* p_node = 0){m_list = p_list;m_node = p_node;}

[Start Func]resets the iterator to point to the very first node in the list

void Start(){if (m_list != 0)m_node = m_list->m_head;}

[Forth Func]

void Forth(){if (m_node != 0)m_node = m_node->m_next;}

[Item Func]

Datatype& Item(){return m_node->m_data;}

[Valid]

bool Valid(){return (m_node != 0);}

[GetIterator]generate a iterator

SListIterator<Datatype> GetIterator()// class SLinkedList{return SListIterator<Datatype>(this, m_head);}

[Using Iterators]

SLinkedList<int> list;list.Append(10);list.Append(20);list.Append(30);SListIterator<int> itr = list.GetIterator();for (itr.Start(); itr.Valid(); itr.Forth()){cout << itr.Item() << ", ";}itr.Start();

[Insert Func] inserts a node after an iterator

void Insert(SListIterator<Datatype>& p_iterator, Datatype p_data){if (p_iterator.m_list != this)return;if (p_iterator.m_node != 0){p_iterator.m_node->InsertAfter(p_data);if (p_iterator.m_node == m_tail){m_tail = p_iterator.m_node->m_next;}m_count ++;}else{Append(p_data);}}

[Remove]

void Remove(SListIterator<Datatype>& p_iterator){SListNode<Datatype>* node = m_head;if (p_iterator.m_list != this)return;if (p_iterator.m_node == 0)return;if (p_iterator.m_node == m_head){p_iterator.Forth();RemoveHead();}else{while (node->m_next != p_iterator.m_node)node = node->m_next;p_iterator.Forth();if (node->m_next == m_tail){m_tail = node;}delete node->m_next;node->m_next = p_iterator.m_node;}m_count --;}

7.Doubly Linked List
[Node Structure]
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8.Real-World Issues
  Don't use linked lists for things that require little processing or things that will be created and destroyed quickly.