双向链表反转

链表节点定义：

struct ListHao { ListHao * prev = nullptr; ListHao * next = nullptr; double element = 0; }; ListHao* ReverseList(ListHao* first); 现要实现输入一个双向链表头指针，反转链表，并返回反转后的头指针。链表节点如下图，关键代码如下：

ListHao* ReverseList(ListHao* head) { if (head == nullptr || head->next == nullptr) { return head; } //Assume that this list is not loop. ListHao *pNode = head, *pPre = nullptr; while (pNode != nullptr) { ListHao* pNext = pNode->next; pNode->next = pPre; pNode->prev = pNext; pPre = pNode; pNode = pNext; } return pPre; }

测试代码：

void main() { ListHao* list = new ListHao(); list->element = rand() / 101; list->prev = nullptr; for (int ii = 0; ii < 5; ii++) { ListHao* temp = new ListHao(); temp->element = rand() / 101; list->next = temp; temp->prev = list; list = temp; } cout << "Backward output:" << endl; cout << list->element << endl; while (list->prev != nullptr) { list = list->prev; cout << list->element << endl; } ListHao* result = ReverseList(list); cout << "Forward output after reverse:" << endl; cout << result->element << endl; while (result->next != nullptr) { result = result->next; cout << result->element << endl; } system("pause"); }