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.
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c++ code:
/**
* 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) return NULL;
// 加一个哑值作为“伪”头结点，方便处理头部有重复结点情况
ListNode dummy(0);
dummy.next = head;
ListNode *pre = &dummy;
ListNode *cur = head;
while(cur){
while(cur->next && cur->val == cur->next->val) cur=cur->next;
if(pre->next == cur) pre = pre->next; // 无重复结点
else pre->next = cur->next; // 有重复结点
cur = cur->next;
}
return dummy.next;
}
};