class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if(head == nullptr) {
            return head;
        }

        ListNode* last = nullptr;
        while(head->next) {
            auto next = head->next;
            head->next = last;
            last = head;
            head = next;
        }
        head->next = last;

        return head;
    }
};