Remove All Elements from Linked List

Given the head of a linked list and an integer val, remove all the nodes of the linked list that have Node.val == val, and return the new head.

Difficulty:

JavaScript Solution

function removeElements(head, val){
  let dummy = new ListNode(0);
  dummy.next = head;
  let current = dummy;
  while(current.next){
    if(current.next.val === val) current.next = current.next.next;
    else current = current.next;
  }
  return dummy.next;
}

Explanation: Use a dummy node to simplify head deletion. Traverse list and skip nodes with given value.

⏱ O(n) | 💾 O(1)

Java Solution

class Solution {
  public ListNode removeElements(ListNode head, int val){
    ListNode dummy = new ListNode(0);
    dummy.next = head;
    ListNode current = dummy;
    while(current.next != null){
      if(current.next.val == val) current.next = current.next.next;
      else current = current.next;
    }
    return dummy.next;
  }
}

Explanation: Dummy node helps handle head removal. Iterate and remove matching nodes.

⏱ O(n) | 💾 O(1)

Python Solution

def remove_elements(head, val):
    dummy = ListNode(0)
    dummy.next = head
    current = dummy
    while current.next:
        if current.next.val == val:
            current.next = current.next.next
        else:
            current = current.next
    return dummy.next

Explanation: Dummy node simplifies removal of head and other nodes with given value.

⏱ O(n) | 💾 O(1)

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Remove All Elements from Linked List