Remove Duplicates from Sorted List II

Remove
Duplicates from Sorted List IIApr
22 '12

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers
from the original list.

For example,

Given

1->2->3->3->4->4->5

,
return

1->2->5

.

Given

1->1->1->2->3

,
return

2->3

.

class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if(head == NULL || head->next == NULL) return head;
ListNode prehead(0);
prehead.next = head;
ListNode *q = &prehead,*p = head;
while((p = p->next)!= NULL)
{
if(p->val != q->next->val){
if(p != q->next->next) q->next = p;
else q = q->next;
}else if (p->next==NULL)
q->next = p->next;
}

return prehead.next;
}
};

60 milli secs