206-reverse-linked-list.cpp

class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        ListNode* p1 = nullptr;
        ListNode* p2 = head;
        while (p2 != nullptr) {
            ListNode* p3 = p2->next;
            p2->next = p1;
            p1 = p2;
            p2 = p3;
        }
        return p1;
    }
};