How to Efficiently Merge K Sorted Lists in Java Without Excessive Memory Usage?
I need some guidance on I've spent hours debugging this and I've looked through the documentation and I'm still confused about I'm working on merging k sorted linked lists into one sorted linked list in Java. My current implementation uses a naive approach where I iterate over each list to find the minimum element, which leads to O(n * k) time complexity, where n is the average length of the lists. Additionally, I'm facing memory issues since I maintain a separate list to hold all the elements before merging them. Here's the code I've tried so far: ```java class ListNode { int val; ListNode next; ListNode(int x) { val = x; } } public class MergeKLists { public ListNode mergeKLists(ListNode[] lists) { if (lists == null || lists.length == 0) return null; ListNode head = new ListNode(0); ListNode current = head; while (true) { ListNode minNode = null; int minIndex = -1; for (int i = 0; i < lists.length; i++) { if (lists[i] != null) { if (minNode == null || lists[i].val < minNode.val) { minNode = lists[i]; minIndex = i; } } } if (minNode == null) break; current.next = minNode; current = current.next; lists[minIndex] = lists[minIndex].next; } return head.next; } } ``` The above code works, but it becomes inefficient for larger values of k (like 1000) and the lists can be quite large as well. I also noticed that the memory consumption spikes when I run it with larger inputs, potentially due to the way I'm managing the linked lists. I'm looking for a more efficient way to perform this merge operation, ideally with a time complexity of O(n log k) and minimizing memory usage. Any suggestions or best practices I can apply here? For context: I'm using Java on macOS. This is part of a larger service I'm building. How would you solve this?