翻转一个链表
您在真实的面试中是否遇到过这个题？
Yes
样例
给出一个链表1->2->3->null，这个翻转后的链表为3->2->1->null
/**
* Definition of ListNode
*
* class ListNode {
* public:
* int val;
* ListNode *next;
*
* ListNode(int val) {
* this->val = val;
* this->next = NULL;
* }
* }
*/
class Solution {
public:
/**
* @param head: The first node of linked list.
* @return: The new head of reversed linked list.
*/
void insert(ListNode * newhead,ListNode * node){
ListNode * q = newhead->next;
newhead->next=node;
node->next=q;
}
ListNode *reverse(ListNode *head) {
// write your code here
if(head==NULL){
return NULL;
}
if(head->next==NULL){
return head;
}
ListNode * newhead=new ListNode();
newhead->next=head;
ListNode * p=head->next;
head->next=NULL;
while(p!=NULL){
ListNode * node =p;
p=p->next;
insert(newhead,node);
}
return newhead->next;
}
};
