Description
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
Solution
Python3
# Definition for singly-linked list.
# 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]:
def reverseLL(node):
prev = None
while node:
nxt = node.next
node.next = prev
prev = node
node = nxt
return prev
head = reverseLL(head)
curr = head
while curr and curr.next:
if curr.val > curr.next.val:
curr.next = curr.next.next
else:
curr = curr.next
return reverseLL(head)