Any idea how to generate null while creating new ListNode?
Problem I am stuck with : https://leetcode.com/problems/merge-k-sorted-lists
Solution I wrote :
public ListNode mergeKLists(ListNode[] lists) {
ListNode fin = new ListNode();
ListNode origHead = fin;
if(lists.length == 0) return null;
while(true) {
int minIndex = -1;
int minValue = Integer.MAX_VALUE;
for(int i=0;i<lists.length;i++) {
if(lists[i] != null && lists[i].val < minValue) {
minIndex = i;
minValue = lists[i].val;
}
}
if(minValue == Integer.MAX_VALUE) return origHead;
lists[minIndex] = lists[minIndex].next;
fin.val = minValue;
fin.next = new ListNode();
fin = fin.next;
}
}For testcase : 
Zero gets added in the ending. I did get rid of it by adding a counter for null but I feel there's a difference in my understanding about ListNode and this is the same issue I had got stuck with earlier as well.
Thanks.
-------EDIT1-------
Came across this approach that finally worked.
public ListNode mergeKLists(ListNode[] lists) {
ListNode fin = new ListNode(0);
ListNode origHead = fin;
if(lists.length == 0) return null;
while(true) {
int minIndex = -1;
int minValue = Integer.MAX_VALUE;
for(int i=0;i<lists.length;i++) {
if(lists[i] != null && lists[i].val < minValue) {
minIndex = i;
minValue = lists[i].val;
}
}
if(minValue == Integer.MAX_VALUE) return origHead.next;
lists[minIndex] = lists[minIndex].next;
fin.next = new ListNode(minValue);
fin = fin.next;
}
}As you can notice, we are returning origHead.next;
And head is default 0. AND, we update our node creation logic to
fin.next = new ListNode(minValue);
fin = fin.next;Comments (0)