83-Remove-Duplicates-from-Sorted-List.md

83. Remove Duplicates from Sorted List

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.

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: ListNode) -> ListNode:
        ans = ListNode(-101, head)
        ptr = ans
        latest = ans
        while ptr.next:
            ptr = ptr.next
            if ptr.val != latest.val:
                latest.next = ptr
                latest = latest.next
        latest.next = None
        return ans.next

Even simpler linked list manipulation.