【双向循环带头链表】

 双向循环带头链表结构如下

 先设计数据结构如下。
typedef int LTDataType;
typedef struct ListNode
{
struct ListNode* prev;
struct ListNode* next;
LTDataType val;
}LTNode;.
  第一个节点为头结点，后面链接的节点存储数据。一个指向前面的指针prev,一个指向后面的指针next，一个数据。

 实现下面的接口
LTNode* ListInit();
void ListDestory(LTNode* phead);
void ListPrint(LTNode* phead);
void ListPushBack(LTNode* phead, LTDataType data);
void ListPopBack(LTNode* phead);
void ListPushFront(LTNode* phead, LTDataType data);
void ListPopFront(LTNode* phead);
LTNode* ListFind(LTNode* phead, LTDataType data);
// 双向链表在pos的前面进行插入
void ListInsert(LTNode* pos, LTDataType data);
// 双向链表删除pos位置的结点
void ListErase(LTNode* pos);
 
LTNode* ListInit();这个节点的实现初始化，要注意，两个指针要自己指向自己，在写后面的接口中有大用.

LTNode* BuyNode(LTDataType data)
{LTNode* node = (LTNode*)malloc(sizeof(LTNode));if (node == NULL){perror("malloc fail");return;}node->prev = node;node->next = node;node->val = data;return node;
}LTNode* ListInit()
{LTNode* node = (LTNode*)malloc(sizeof(LTNode));if (node == NULL){perror("malloc fail");return;}node->prev = node->next = node;return node;
}
}

 ListDestory接口实现定义一个指针cur = phead->next,先保存下一个节点的地址，在free.

void ListDestory(LTNode* phead)
{assert(phead);LTNode* cur = phead->next;while (cur!=phead){LTNode* next = cur->next;free(cur);cur = next;}free(phead);phead = NULL;
}

 ListPrint,遍历直接·打印

void ListPrint(LTNode* phead)
{assert(phead);LTNode* cur = phead->next;while (cur!=phead){printf("%d->", cur->val);cur = cur->next;}printf("\n---------------------------\n");
}

 LIstPushBack直接尾插，

void ListPushBack(LTNode* phead, LTDataType data)
{assert(phead);LTNode* newnode = BuyNode(data);LTNode* tail = phead->next;while (phead != tail->next)找到尾直接插入{tail = tail->next;}LTNode* prev = tail;LTNode* next = tail->next;prev->next = newnode;newnode->prev = prev;newnode->next = next;next->prev = newnode;
}

 尾删

void ListPopBack(LTNode* phead)
{assert(phead);if (phead->next == phead){printf("No node\n");return;}LTNode* cur = phead->next;while (cur->next != phead){cur = cur->next;}LTNode* prev = cur->prev;LTNode* next = cur->next;free(cur);prev->next = next;next->prev = prev;
}

 头插

void ListPushFront(LTNode* phead, LTDataType data)
{assert(phead);LTNode* newnode = BuyNode(data);LTNode* next = phead->next;phead->next = newnode;newnode->prev = phead;newnode->next = next;next->prev = newnode;
}

 头删

void ListPopFront(LTNode* phead)
{assert(phead);if (phead->next == phead){printf("No node\n");return;}LTNode* del = phead->next;LTNode* next = del->next;free(del);del = NULL;phead->next = next;next->prev = phead;}

 下面接口

LTNode* ListFind(LTNode* phead, LTDataType data)
{assert(phead);LTNode* cur = phead->next;while (cur != phead){if (cur->val == data){return cur;}cur = cur->next;}
}// 双向链表在pos的前面进行插入
void ListInsert(LTNode* pos, LTDataType data)
{assert(pos);LTNode* newnode = BuyNode(data);LTNode*  prev = pos->prev;prev->next = newnode;newnode->prev = prev;newnode->next = pos;pos->prev = newnode;}
// 双向链表删除pos位置的结点
void ListErase(LTNode* pos)
{assert(pos);LTNode* prev = pos->prev;LTNode* next = pos->next;free(pos);pos = NULL;prev->next = next;next->prev = prev;
}

 完结！