# Why not merge sorted lists iteratively?

• I'm getting time out error for the below code. Can you help me understand what's wrong if we merge the list in the loop rather than the partition technique?

``````public ListNode mergeKLists(ListNode[] lists) {
if (lists == null || lists.length == 0) {
return null;
}
int len = lists.length;
for (int i = 0; i < len; i++) {
}
//return partition(lists, 0, lists.length-1);
}

public ListNode partition(ListNode[] lists, int start, int end) {
if (start > end) {
return null;
}
if (start == end) {
return lists[start];
}
int mid = start + (end-start)/2;
ListNode l1 = partition(lists, start, mid);
ListNode l2 = partition(lists, mid+1, end);
return merge(l1, l2);
}

public ListNode merge(ListNode l1, ListNode l2) {
if (l1 == null) {
return l2;
}
if (l2 == null) {
return l1;
}

if (l1.val < l2.val) {
l1.next = merge(l1.next, l2);
return l1;
} else {
l2.next = merge(l1, l2.next);
return l2;
}
}``````

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