尾插
ListNode* BuyListNode(LTDataType x) { ListNode* newnode = (ListNode*)malloc(sizeof(ListNode)); if (newnode == NULL) { return; } newnode->data = x; newnode->next = NULL; newnode->prev = NULL; return newnode; } void ListPushBack(ListNode* phead, LTDataType x) { ListNode* tail = phead->prev; ListNode* newnode = BuyListNode(x); tail->next = newnode; newnode->prev = tail; newnode->next = phead; phead->prev = newnode; }
尾删
void ListPopBack(ListNode* phead) { assert(phead); assert(phead->next != phead); ListNode* tail = phead->prev; ListNode* prev = tail->prev; prev->next = phead; phead->prev = prev; free(tail); tail = NULL; }
头插：
ListNode* BuyListNode(LTDataType x) { ListNode* newnode = (ListNode*)malloc(sizeof(ListNode)); if (newnode == NULL) { return; } newnode->data = x; newnode->next = NULL; newnode->prev = NULL; return newnode; } void ListPushFront(ListNode* phead, LTDataType x) { assert(phead); ListNode* first = phead->next; ListNode* newnode = BuyListNode(x); phead->next = newnode; newnode->prev = phead; newnode->next = first; first->prev = newnode; }
头删：
void ListPopFront(ListNode* phead) { assert(phead); assert(phead->next != phead); ListNode* first = phead->next; ListNode* second = first->next; phead->next = second; second->prev = phead; free(first); first = NULL; }
打印：
void ListPrint(ListNode* phead) { ListNode* cur = phead->next; while (cur != phead) { printf("%d ", cur->data); cur = cur->next; } printf("\n"); }
查找：
ListNode* ListFind(ListNode* phead, LTDataType x) { assert(phead); ListNode* cur = phead->next; while (cur != phead) { if (cur->data == x) { return cur; } cur = cur->next; } return NULL; }
cur指向第一个结点，当结点的数据域不等于x，就去看下一个结点，要是最后找到phead都没有找到，就说明没有.
在某个结点前插入一个结点：
void ListInsert(ListNode* pos, LTDataType x) { assert(pos); ListNode* newnode = BuyListNode(x); ListNode* prev = pos->prev; prev->next = newnode; newnode->prev = prev; newnode->next = pos; pos->prev = newnode; }
删除某个结点：
void ListErase(ListNode* pos) { assert(pos); ListNode* prev = pos->prev; ListNode* next = pos->next; prev->next = next; next->prev = prev; free(pos); pos = NULL; }
销毁链表：
void ListDestory(ListNode* phead) { assert(phead); ListNode* cur = phead->next; while (cur != phead) { ListNode* next = cur->next; free(cur); cur = next; } free(phead); phead = NULL; }
