21. Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

public class Solution{
public ListNode mergeTwoLists(ListNode l1, ListNode l2){
ListNode start;
if (l1 == null)
return l2;
if (l2 == null)
return l1;
//对输入进行最简单的判断，这已经是一个必须的步骤了~
if (l1.val < l2.val){
start = l1;
start.next = mergeTwoLists(l1.next, l2);
} else {
start = l2;
start.next = mergeTwoLists(l1, l2.next);
}
//对数据判断然后递归~
return start;
}
}

又是一道水题~