双指针法实现

class Solution {
public:
    ListNode* ReverseList(ListNode* pHead) {
        ListNode* cur = pHead;
        ListNode* pre = nullptr;
        while(cur != nullptr){
            ListNode* temp = cur->next;
            cur->next = pre;
            pre = cur;
            cur = temp;
        }
        return pre;
    }
};