LeetCode 206. Reverse Linked List

解题思路: 使用两个指针,分别指向head 和 head->next,或者直接递归.

class Solution {
public:
ListNode* reverseList(ListNode* head) {
ListNode* p1 = NULL;
ListNode* p2 = NULL;
while(head){
p1 = head->next;
head->next = p2;
p2 = head;
head = p1;
}
return p2;
}
};

ListNode* reverseList(ListNode* head) {
if(!head || !(head->next)) return head;
ListNode* res = reverseList(head->next);
head->next->next = head;
head->next = NULL;
return res;
}