单链表反转

来源：互联网发布：js中gbk编码转换utf8 编辑：程序博客网时间：2024/05/12 02:08

struct ListNode
{
int key;
ListNode* next;
};

1.使用三个指针遍历单链表，逐个链接点进行反转

ListNode* ReverseList(ListNode* head)
{
         ListNode* p;
         ListNode* q;
         ListNode* r;

if (head == NULL || head->next == NULL)
return head;

         p = head;
         q = p->next;
         p->next == NULL;
         while (q != NULL)
         {
                  r = q->next;
                  q->next = p;
                  p = q;
                  q = r;
         }

         return p;
}
ListNode* Reverse(ListNode* head)
{
         ListNode* pNode = head;
         ListNode* pPrev = NULL;

         while (pNode != NULL)
         {
                   ListNode* pNext = pNode->next;

                    if (pNext == NULL)
                    {
                             return pNode;
                    }
                    pNode->next = pPrev;
                    pPrev = pNode;
                    pNode = pNext;
         }
}

2.从第2个节点到第N个节点，依次逐节点插入到第1个节点(head节点)之后，最后将第一个节点挪到新表的表尾。

ListNode* ReverseList(ListNode* head)
{
ListNode* pNode;
ListNode* pNext;

if (head==NULL || head->next==NULL)
return head;

          pNode = head->next;
          pNext = pNode->next;
          while (pNext != NULL)
          {
                    pNode->next = pNext->next;
                    pNext->next = head->next;
                    head->next = pNext;
                    pNext = pNode->next;
          }
          pNode->next = head;
          pNext = head->next;
          head->next = NULL;

return pNext;
}