Middle of the Linked List Easy 0 attempts
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Middle of the Linked List

Easy Linked List LeetCode

You get the head of a singly linked list. Return the middle node. If the number of nodes is even, there are two middle positions; return the second of those (the one closer to the tail).

Return the node itself. The examples display the suffix beginning at that node.

Input Format
Implement middleNode(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 ยท Run Sample

Input
head = [1,2,3,4,5]
Output
[3,4,5]

Example 2

Input
head = [1,2,3,4,5,6]
Output
[4,5,6]
Constraints
  • 1 to 100 nodes
  • 1 <= Node.val <= 100
Test Cases (2)
Case 1
Args: [[1,2,3,4,5]] Expected: [3,4,5]
Case 2
Args: [[1,2,3,4,5,6]] Expected: [4,5,6]
Topics
Linked List

Slow and Fast Pointers

javascript
function middleNode(head) {
  let slow = head, fast = head;
  while (fast && fast.next) { slow = slow.next; fast = fast.next.next; }
  return slow;
}

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

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JavaScript