LeetCode "Remove Nth Node From End of List"

class Solution {
public:
    ListNode *removeNthFromEnd(ListNode *head, int n) {
        
        ListNode *p = NULL;
        ListNode *p0 = head;
        ListNode *p1 = head;
        ListNode *pre1 = NULL;
        while (--n)        p0 = p0->next;
        
        while (p0->next)
        {
            p0 = p0->next;
            pre1 = p1;
            p1 = p1->next;
        }
        if (p1 == head) p = head->next;
        else
        {
            pre1->next = p1->next;
            p = head;
        }
        return p;
    }
};