82. Remove Duplicates from Sorted List II
Medium
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.
# 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: Optional[ListNode]) -> Optional[ListNode]:
if not head: # no element
return head
elif head.next == None: # 1 element
return head
elif head.next.next == None: # 2 elements
if head.val == head.next.val:
return None
else:
return head
prev = head
s_head = ListNode(0, prev)
old = s_head
node = prev.next
delete = False
while node:
if prev.val == node.val:
delete = True
node = node.next
if node == None:
old.next = None
else:
if delete:
old.next = node
prev = node
node = node.next
delete = False
else:
old = prev
prev = node
node = node.next
return s_head.next