2487. Remove Nodes From Linked List

#### QUESTION:

Remove every node which has a node with a strictly greater value anywhere to the right side of it.

Example 1:

``````Input: head = [5,2,13,3,8]
Output: [13,8]
Explanation: The nodes that should be removed are 5, 2 and 3.
- Node 13 is to the right of node 5.
- Node 13 is to the right of node 2.
- Node 8 is to the right of node 3.
``````

Example 2:

``````Input: head = [1,1,1,1]
Output: [1,1,1,1]
Explanation: Every node has value 1, so no nodes are removed.
``````

Constraints:

``````The number of the nodes in the given list is in the range [1, 105].
1 <= Node.val <= 105
``````

#### SOLUTION:

``````/**
* public class ListNode {
*     public var val: Int
*     public var next: ListNode?
*     public init() { self.val = 0; self.next = nil; }
*     public init(_ val: Int) { self.val = val; self.next = nil; }
*     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
* }
*/
class Solution {
func removeNodes(_ head: ListNode?) -> ListNode? {