this is merging two ordered list of recursive code, the iteration will write, recursive write wrong,
This is the official LeetCode solutions, problem:
Behind the two else if why want to write the return on the inside, and l1. Next=mergeTwoLists (l1. Next, l2); Why is the l1. Next?
If it is not in the l1. Val? This code is how to deal with a linked list is finished, another list hasn't finish comparing?
Please advise

 
The class Solution {
Public ListNode mergeTwoLists (ListNode ListNode l1, l2) {
If (l1==null) {
Return l2; 
} else if (l2==null) {
Return l1. 
} else if (l1. Val & lt; L2. Val) {
L1. Next=mergeTwoLists (l1. Next, l2); 
Return l1. 
} else {
L2. Next=mergeTwoLists (l1 and l2. Next); 
Return l2; 
} 

} 
}