Remove Duplicates from Sorted Linked List

83. Remove Duplicates from Sorted List

Easy

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Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.

 

Example 1:

Input: head = [1,1,2]
Output: [1,2]

Example 2:

Input: head = [1,1,2,3,3]
Output: [1,2,3]

 

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.

Python solution

# Definition for singly-linked list.
class ListNode:
     def __init__(self, val=0, next=None):
            self.val = val
            self.next = next
class Solution:
    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:

        current = head

        if head is None:
            return None

        while current.next:
            if current.val == current.next.val:
                next_element = current.next.next
                current.next = next_element
            else:
                current = current.next

        return head
#end

The time complexity of the above solution is O(n), where n is the total number of nodes in the linked list.