remove-nodes-from-linked-list_2487.py

# You are given the head of a linked list.

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

# Return the head of the modified linked list.

# 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

# ---------------------------------------Runtime 396 ms Beats 97.57% Memory 62.94 MB Beats 60.07%---------------------------------------

from typing import Optional


class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next


class Solution:
    def removeNodes(self, head: Optional[ListNode]) -> Optional[ListNode]:
        if head is None:
            return head
        head.next = self.removeNodes(head.next)
        if head.next and head.val < head.next.val:
            return head.next
        return head