Remove Duplicates from Sorted Linked List

Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.

Difficulty:

JavaScript Solution

function deleteDuplicates(head){
  let current = head;
  while(current && current.next){
    if(current.val === current.next.val) current.next = current.next.next;
    else current = current.next;
  }
  return head;
}

Explanation: Iterate through the list, if current node value equals next node value, skip the next node.

⏱ O(n) | 💾 O(1)

Java Solution

class Solution {
  public ListNode deleteDuplicates(ListNode head){
    ListNode current = head;
    while(current != null && current.next != null){
      if(current.val == current.next.val) current.next = current.next.next;
      else current = current.next;
    }
    return head;
  }
}

Explanation: Traverse list and remove nodes with duplicate values in-place.

⏱ O(n) | 💾 O(1)

Python Solution

def delete_duplicates(head):
    current = head
    while current and current.next:
        if current.val == current.next.val:
            current.next = current.next.next
        else:
            current = current.next
    return head

Explanation: Check each node with next node and remove duplicates iteratively.

⏱ O(n) | 💾 O(1)

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Remove Duplicates from Sorted Linked List