876.-middle-of-the-linked-list.md

876. Middle of the Linked List

Given the head of a singly linked list, return the middle node of the linked list.

If there are two middle nodes, return the second middle node.

Example 1:

Input: head = [1,2,3,4,5]
Output:
 [3,4,5]
Explanation:
 The middle node of the list is node 3.

Example 2:

Input: head = [1,2,3,4,5,6]
Output:
 [4,5,6]
Explanation:
 Since the list has two middle nodes with values 3 and 4, we return the second one.

Constraints:

• The number of nodes in the list is in the range [1, 100].
• 1 <= Node.val <= 100

TypeScript

Result

Runtime: 110 ms, faster than 33.94% of TypeScript online submissions for Middle of the Linked List.

Memory Usage: 42.5 MB, less than 94.79% of TypeScript online submissions for Middle of the Linked List.

const middleNode = (head: ListNode | null): ListNode | null => {
    let slow: ListNode | null = head, fast: ListNode | null = head

    while (fast && fast.next) {
        slow = slow.next
        fast = fast.next.next
    }
    return slow
}

Python

Result

Runtime: 36 ms, faster than 86.93% of Python3 online submissions for Middle of the Linked List.

Memory Usage: 13.8 MB, less than 55.04% of Python3 online submissions for Middle of the Linked List.

class Solution:
    def middleNode(self, head: Optional[ListNode]) -> Optional[ListNode]:
        slow = fast = head
        while fast and fast.next:
            slow, fast = slow.next, fast.next.next
        return slow

PHP

Result

Runtime: 6 ms, faster than 83.74% of PHP online submissions for Middle of the Linked List.

Memory Usage: 19.4 MB, less than 14.19% of PHP online submissions for Middle of the Linked List.

class Solution
{
    /**
     * @param ListNode|null $head
     * @return ListNode|null
     */
    function middleNode(?ListNode $head): ?ListNode
    {
        $slow = $fast = $head;
        while ($fast && $fast->next) {
            list($slow, $fast) = array($slow->next, $fast->next->next);
        }
        return $slow;
    }
}