【LeetCode 234_链表】Palindrome Linked List

 1 ListNode* ReverseList(ListNode *p) {

 2     if (p == NULL || p->next == NULL)

 3         return p;

 4 

 5     ListNode *pre = NULL;

 6     ListNode *next = p->next;

 7     while (p) {

 8         p->next = pre;

 9         pre = p;

10         p = next;

11         next = p ? p->next : NULL;

12     }

13     return pre;

14 }

15 

16 bool isPalindrome(ListNode* head) {

17     if (head == NULL || head->next == NULL)

18         return true;

19     ListNode *slow = head, *fast = head;

20     while (fast->next && fast->next->next) {

21         slow = slow->next;

22         fast = fast->next->next;

23     }

24     slow->next = ReverseList(slow->next);

25     slow = slow->next;

26 

27     while (slow) {

28         if (slow->val != head->val)

29             return false;

30         slow = slow->next;

31         head = head->next;

32     }

33     return true;

34 }