题解 | #链表的回文结构#

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};*/
class PalindromeList {
  public:
    struct ListNode* reverseList(struct ListNode* head) {
        struct ListNode* cur = head;
        struct ListNode* rhead = NULL;

        while (cur) {
            struct ListNode* next = cur->next;
            // 头插
            cur->next = rhead;
            rhead = cur;
            //迭代
            cur = next;
        }
        return rhead;
    }

    struct ListNode* middleNode(struct ListNode* head) {
        struct ListNode* fast = head, *slow = head;
        while (fast && fast->next) {
            slow = slow->next;
            fast = fast->next->next;
        }
        return slow;
    }


    bool chkPalindrome(ListNode* head) {
        // write code here
        struct ListNode *mid = middleNode(head);
        struct ListNode *rmid = reverseList(mid);
        while (rmid)
        {
            if (rmid->val != head->val)
            {
                return false;
            }
            else 
            {
                rmid = rmid->next;
                head = head->next;
            }
        }
        return true;
    }
};