21_Merge Two Sorted Lists

/*
21. Merge Two Sorted Lists
Runtime: 0 ms, faster than 100.00% of Java online submissions for Merge Two Sorted Lists.
Memory Usage: 39.1 MB, less than 70.60% of Java online submissions for Merge Two Sorted Lists.

 */
class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        
        //edge case 1
        if(l1==null && l2==null)
            return null;
        
        //edge case 2
        if(l1==null)
            return l2;      
        if(l2==null)
            return l1;
        
        //creating a new linkedList to save result
        ListNode output=new ListNode(0) ;
            ListNode temp=output;
        
        //comparing and adding nodes to the our output list
        while(l1!=null && l2!=null)
        {
            if(l1.val<=l2.val)
            {
                output.next=l1;
                
                l1=l1.next;
            }else{
                output.next=l2;
                
                l2=l2.next;
            }
          
            output=output.next;
        }
        
        
        //adding any leftout nodes
        while(l1!=null)
        {
            output.next=l1;
            l1=l1.next;
            output=output.next;
        }
        
        while(l2!=null)
        {
            output.next=l2;
            l2=l2.next;
            output=output.next;
        }
        
        //returning our output
        return temp.next;
        
        
    }
}