[LeetCode] Remove Duplicates from Sorted List、Remove Duplicates from Sorted List II

Remove Duplicates
from Sorted List:

Given a sorted linked list, delete all duplicates such that each element appear only once.

For example,

Given

1->1->2

,
return

1->2

.

Given

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

,
return

1->2->3

.

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
#define LN ListNode
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
// Start typing your C/C++ solution below
// DO NOT write int main() function

const int INVALID =INT_MAX;
LN guard(INVALID);
guard.next=head;
LN* pre=&guard;
LN* cur=head;
while(cur)
{
if ( cur->val == pre->val )
{
pre->next=cur->next;
delete cur;
cur=pre->next;
}
else
{
pre=pre->next;
cur=cur->next;
}
}
return guard.next;
}
};

Remove Duplicates
from Sorted List II：

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

.

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
#define LN ListNode
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
// Start typing your C/C++ solution below
// DO NOT write int main() function

const int INVALID=INT_MAX;
LN guard(INVALID);
guard.next=head;

LN* pTail=&guard;
LN* cur=head;
while(cur)
{
if ( cur->next==NULL || cur->val!=cur->next->val)
{
pTail->next=cur;
pTail=pTail->next;
cur=cur->next;
}
else
{
int v=cur->val;
while(cur&&cur->val==v)
{
pTail->next=cur->next;
delete cur;
cur=pTail->next;
}
}
}
return guard.next;
}
};