题目：
Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
Example
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.
题解：
Solution 1 ()
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
if (head == nullptr) {
return head;
}
ListNode* dummy = new ListNode(-);
dummy->next = head;
head = dummy;
while (head->next != nullptr && head->next->next != nullptr) {
if (head->next->val == head->next->next->val) {
int value = head->next->val;
while (head->next != nullptr && head->next->val == value) {
head->next = head->next->next;
}
} else {
head = head->next;
}
}
return dummy->next;
}
};二级指针
Solution 2 （）
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
if (head == nullptr || head->next == nullptr) {
return head;
}
ListNode **t = &head;
while (*t) {
if ((*t)->next && (*t)->next->val == (*t)->val) {
ListNode *tmp = *t;
while (tmp && (*t)->val == tmp->val) {
tmp = tmp->next;
}
*t = tmp;
} else {
t = &((*t)->next);
}
}
return head;
}
};