Merge k Sorted Lists

var mergeKLists = function (lists) {
  lists = lists.filter((list) => list);

  if (lists.length === 0) {
    return null;
  }

  const list = new ListNode();
  let next = list;

  while (lists.length > 0) {
    let min = 0;

    for (let i = 0; i < lists.length; i++) {
      if (lists[i] && lists[i].val < lists[min].val) {
        min = i;
      }
    }

    next.val = lists[min].val;
    lists[min] = lists[min].next;

    if (!lists[min]) {
      lists.splice(min, 1);
    }

    if (lists.length > 0) {
      next.next = new ListNode();
      next = next.next;
    }
  }

  return list;
};