Remove Duplicates from Sorted List Easy 0 attempts
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Remove Duplicates from Sorted List

Easy Linked List LeetCode

You're given the head of a singly linked list whose values are already arranged in non-decreasing order. Delete duplicate values so each distinct value remains only once, keeping the list sorted, and return the head of the updated list.

Solve it in place — reuse the existing nodes and simply adjust their pointers rather than building a new list.

Input Format
Implement deleteDuplicates(head). Inputs below show JavaScript function arguments; there is no stdin parsing. Linked lists use value arrays. The editor passes nodes with val and next properties; [] becomes null.
Output Format
Return the result described in the statement. Returned list heads are displayed as value arrays; a null head is [].

Sample Input and Output

Example 1 · Run Sample

Input
head = [1,1,2,3,3]
Output
[1,2,3]

Example 2

Input
head = []
Output
[]
Constraints
  • 0 to 300 nodes
  • -100 <= Node.val <= 100
  • List is sorted in ascending order
Test Cases (2)
Case 1
Args: [[1,1,2,3,3]] Expected: [1,2,3]
Case 2
Args: [[]] Expected: []
Topics
Linked List

One Pass

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

Time: O(n) | Space: O(1)

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JavaScript