# LeetCode 82. Remove Duplicates from Sorted List II

## Description

https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/

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.

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]
```

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.

## Explanation

We can count the node value occurrences first and then remove those nodes with duplicated values.

## 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: ListNode) -> ListNode:
counter = {}

dummy = ListNode(0)

prev = dummy