## 83. Remove Duplicates from Sorted List

### Easy

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.

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