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203. Remove Linked List Elements

Linked List Recursion

Problem - Remove Linked List Elements

Easy

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 = 6
Output: [1,2,3,4,5]

Example 2:

Input: head = [], val = 1
Output: []

Example 3:

Input: head = [7,7,7,7], val = 7
Output: []

 

Constraints:

  • The number of nodes in the list is in the range [0, 104].
  • 1 <= Node.val <= 50
  • 0 <= val <= 50

Solutions

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# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def removeElements(self, head: Optional[ListNode], val: int) -> Optional[ListNode]:
        if not head:
            return None

        dummy = ListNode(-1, head)
        last = dummy

        while last.next:
            if last.next.val != val:
                last = last.next
            else:
                last.next = last.next.next

        return dummy.next

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 19.6 MB (82.06%)