LeetCode "Remove Duplicates from Sorted List"

class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
if(!head) return NULL;

ListNode *p  = head;
ListNode *p0 = p->next;
while(p && p0)
{
while(p && p0 && p->val == p0->val)
{
p->next = p0->next;
p0 = p0->next;
}

p = p0;
if(p0) p0 = p0->next;
}

return head;
}
};