[LeetCode] 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

.

class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
ListNode *ptr = NULL;
ListNode *cur = head;
ListNode *head0 = NULL;
int cnt = 0;
while(cur != NULL){
ListNode *tmp = cur;
while(cur -> next != NULL && cur -> next -> val == cur -> val)
cur = cur -> next;
if(tmp == cur){
cnt ++;
if(cnt == 1) head0 = ptr = cur;
else {
ptr -> next = cur;
ptr = ptr -> next;
}
}
cur = cur -> next;
if(cnt >= 1)
ptr -> next = NULL;//如出现 1 2 2 2 这种情况，所以要把ptr -> next 设为NULL;
}
if(cnt == 0) return NULL;
return head0;
}
};