如何在不更改C++中的原始链表的情况下反转链表

我正在尝试测试链表是否是回文。为此，我只需反转链表，然后在循环中逐个检查每个节点。但是，我不知道如何按值传递原始链表。我想现在我正在通过它的引用传递链表，它在我反转后修改了原始结构。

 /**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if(!head) return NULL;
        ListNode* current = head;
        ListNode* pre = NULL;
        ListNode* nextTemp = NULL;
        while(current!=NULL) {
            nextTemp = current->next;
            current->next = pre;
            pre = current;
            current = nextTemp;
        }
        head = pre;
        return head;
    }
    bool isPalindrome(ListNode* head) {
        ListNode* original = head;
        ListNode* reverse = reverseList(head);// is there a way that I can pass it as a copy?
        while(original!=NULL){
            if(reverse->val == original->val){
                reverse=reverse->next;
                original=original->next;
            }else{
                return false;
            }
        }
        return true;
    }
};