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import { ListNode } from "../mod.ts";
export default function deleteMiddle(head: ListNode | null): ListNode | null {    const dummy = new ListNode();    dummy.next = head;    let slow: ListNode | null = dummy;    let fast: ListNode | null = dummy;    while (fast && fast.next && slow && fast.next.next) {        slow = slow.next;        fast = fast.next.next;    }    if (slow) {        slow.next = slow.next?.next ?? null;    }    return dummy.next;}