Remove Every Repeated-Value Run from a Sorted List
Company: Amazon
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Other
### Problem
Given the head of a sorted singly linked list, remove every node whose value appears more than once in the original list. Return the head of the sorted list containing only values that originally occurred exactly once. A repeated value contributes no surviving node.
The supplied `ListNode` has `val` and `next` fields. Preserve its pointer interface:
```cpp
ListNode* deleteDuplicates(ListNode* head);
```
Brackets display a chain's values, not an array argument or array return.
### Examples
```text
Input: head = [-2,-2,0,3,3,8]
Output list: [0,8]
```
```text
Input: head = [4,4]
Output list: []
```
### Constraints
- The list has between 0 and 300 nodes.
- Node values are between -100 and 100, inclusive.
- The input is sorted in ascending order, with equal values allowed.
Overview: Remove every repeated-value run from a sorted linked list, leaving only values that originally appeared once.
