链表的回文结构_牛客题霸_牛客网 (nowcoder.com)   (点击前面链接即可查看题目)

reverseList函数请参考:反转链表 - 力扣（LeetCode）C语言-CSDN博客

middleNode函数请参考:链表的中间结点 - 力扣（LeetCode）C语言-CSDN博客

链表:1->2->3->2->1

        先找到中间结点, 也就是3,然后反转3->2->1,但是要注意标红的2仍旧指向3,

所以链表变成了1->2->3<-2<-1,就成了这样.

/*
struct ListNode {int val;struct ListNode *next;ListNode(int x) : val(x), next(NULL) {}
};*/
class PalindromeList {public:struct ListNode* reverseList(struct ListNode* head) {if (head == NULL)return NULL;else {struct ListNode* oldhead = head;struct ListNode* newhead = NULL;while (oldhead) {struct ListNode* nextnode = oldhead->next;oldhead->next = newhead;newhead = oldhead;//迭代oldhead = nextnode;}return newhead;}}struct ListNode* middleNode(struct ListNode* head) {struct ListNode* slow = head;struct ListNode* fast = head;//空指针if (NULL == head) {return NULL;}//一个结点else if (NULL == head->next) {return head;}//大于等于2个结点else {while (fast) {if (NULL == fast->next) {return slow;}slow = slow->next;fast = fast->next->next;}return slow;}}bool chkPalindrome(ListNode* A) {// write code hereListNode* mid = middleNode(A);ListNode* rmid = reverseList(mid);while(rmid){if(rmid->val != A->val){return false;}else{rmid = rmid->next;A = A->next; }}return true;}
};