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) {}
* };
*/
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
if (head == nullptr || head->next == nullptr)
return head;
ListNode dummy(-);
dummy.next = head;
ListNode *prev = &dummy, *cur = head;
while (cur != nullptr) {
bool flag = false;
while (cur->next != nullptr && cur->val == cur->next->val) {
flag = true;
prev->next = cur->next;
delete cur;
cur = prev->next;
}
if (flag) {
prev->next = cur->next;
delete cur;
cur = prev->next;
} else {
prev = cur;
cur = cur->next;
}
}
return dummy.next;
}
};