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
My Accepted Solution
n is the number of nodes in m_head
Time complexity: O(n)
Space complexity: O(1)
// Iteration
class Solution {
public:
// ListNode* deleteDuplicates(ListNode* head)
ListNode* deleteDuplicates(ListNode* m_head) {
ListNode* guardHead = new ListNode();
guardHead->next = m_head;
for (auto iter = guardHead, nextNode = guardHead->next; iter->next;
nextNode = nextNode->next) {
while (nextNode->next && nextNode->val == nextNode->next->val) {
nextNode = nextNode->next;
}
if (iter->next == nextNode) {
iter = iter->next;
} else {
iter->next = nextNode->next;
}
}
return guardHead->next;
}
};