3.如果链表中存在pre->val==crur->val -------->判断cur->next==NULL, prev->next==NULL ------>cur->next!=NULL prev->next=cur->next
/**
* 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) {
//判断head 是否为空
if(head==NULL || head->next==NULL) return head;
//迭代法
ListNode* prev=head;
ListNode* cur=head->next;
while(prev->next!=NULL)
{
if(prev->val==cur->val)//元素重复
{
if(cur->next==NULL)
prev->next=NULL;
else
{
prev->next=cur->next;
cur=cur->next;
}
//prev->next=cur->next;
//delete cur;
}
else
{
prev=cur;
cur=cur->next;
}
}
return head;
}
};
