LeetCode Remove Duplicates from Sorted List II
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* deleteDuplicates(ListNode* head) {
if(head==NULL || head->next==NULL)
return head;
ListNode * current=head->next;
ListNode * p=NULL;
ListNode * prev=head;
while(current!=NULL){
if(current->val==prev->val)
{
prev=current;
current=current->next;
}
else
{
if(p!=NULL)
{
if(p->next!=prev)
p->next=current;
else
p=prev;
}
else
{
if(prev->val==head->val && prev!=head)
{
head=current;
p=NULL;
}
else
p=prev;
}
prev=current;
current=current->next;
}
}
if(p==NULL && prev!=head && prev->val==head->val)
return NULL;
else if(p!=NULL){
if(p->next!=prev)
p->next=current;
}
return head;
}
};
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