[leetcode]Remove Duplicates from Sorted List II

问题描述：

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

.

基本思路：

设定一个标志是否是重复数字的变量isrepeat，当前和后一个一样就将isrepeat置true。 然后将isrepeat的节点删除，留下不重复节点。

代码：

ListNode *deleteDuplicates(ListNode *head) {  //C++
if(head == NULL || head->next == NULL)
return head;

ListNode tmphead(0);
tmphead.next= head;

ListNode* pre = &tmphead;
ListNode* tmp = head;

bool isRepeat = false;
while(tmp->next != NULL)
{
if(tmp->val == tmp->next->val)
{
isRepeat = true;
}
else
{
if(isRepeat)
{
isRepeat = false;
}
else
{
pre->next = tmp;
pre = tmp;
}
}
tmp = tmp->next;
}
if(!isRepeat)
{
pre->next = tmp;
pre = tmp;
}
pre->next = NULL;
return tmphead.next;
}