# 21. Merge Two Sorted Lists

21. Merge Two Sorted Lists

```/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
if (l1 == null && l2 == null) return null;
if (l1 == null) return l2;
if (l2 == null) return l1;
ListNode out = null;
ListNode current = null;
if(l1.val == l2.val) {
out =new ListNode(l1.val);
l1 = l1.next;
out.next = new ListNode(l2.val);
l2 = l2.next;
current = out.next;
}else
if(l1.val < l2.val) {
out =new ListNode(l1.val);
l1 = l1.next;
current = out;
}
else {
out =new ListNode(l2.val);
l2 = l2.next;
current = out;
}
while(l1 != null || l2 != null) {
if(l1 == null && l2 == null)
return out;
else if (l1 == null && l2 != null) {
current.next = l2;
return out;
}
else if ( l1 != null && l2 == null) {
current.next = l1;
return out;
}
else if (l1.val  l2.val) {
ListNode newListNode = new ListNode(l2.val);
current.next = newListNode;
current = current.next;
l2 = l2.next;
}
}
return out;
}

}
```