82. Remove Duplicates from Sorted List II
1. Description
Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.
2. Example
Example 1
Input: head = [1,2,3,3,4,4,5]
Output: [1,2,5]
Example 2
Input: head = [1,1,1,2,3]
Output: [2,3]
3. Constraints
- The number of nodes in the list is in the range [0, 300].
- -100 <= Node.val <= 100
- The list is guaranteed to be sorted in ascending order.
4. Solutions
Linked List
n is the number of nodes in head
Time complexity: O(n)
Space complexity: O(1)
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
ListNode dummy;
ListNode *iter = &dummy;
while (head != nullptr) {
if (head->next != nullptr && head->val == head->next->val) {
int value = head->val;
while (head != nullptr && head->val == value) {
head = head->next;
}
} else {
iter->next = head;
iter = iter->next;
head = head->next;
}
}
iter->next = nullptr;
return dummy.next;
}
};