反转链表

`/**

• Definition for singly-linked list.
• struct ListNode {

• int val;
  

• struct ListNode *next;
  

• };
  */

struct ListNode* reverseList(struct ListNode* head){
struct ListNode* newhead = NULL,tmp;
while(head){
/ tmp = head->next;
head->next = newhead;
newhead = head;
head = tmp;//保存head->next,接下来将1独立拿出来，head->next = NULL;*/
tmp = head;
head = head->next;
tmp->next = newhead;
newhead = tmp;
}
return newhead;
}`
如果tmp = head->next和tmp = head区别在于前者保存了下一个结点，而后者是暂存当前结点，所以后者不能上来就head->next = newhead，会丢失后面下一个结点。
两个写法的newhead含义恰恰相反，前者newhead是暂存当前结点，后者由于头节点已经向后移动了，导致newhead暂存的是下一结点。