動機
複習Linked list的remove
Problem
Given the head
of a linked list and an integer val
, remove all the nodes of the linked list that has Node.val == val
, and return the new head.
Example 1:
Input: head = [1,2,6,3,4,5,6], val = 6Output: [1,2,3,4,5]
Example 2:
Input: head = [], val = 1Output: []
Example 3:
Input: head = [7,7,7,7], val = 7Output: []
Constraints:
- The number of nodes in the list is in the range
[0, 104]
. 1 <= Node.val <= 50
0 <= val <= 50
Sol
class Solution:
def removeElements(self, head: ListNode, val: int) -> ListNode:
if head:
prev, ret = None, head
while ret and ret.val == val:
ret = ret.next
cur = ret
while cur:
if cur.val == val:
prev.next = cur.next
else:
prev = cur
cur = cur.next
return ret
else:
return head