Add Two Numbers --- LeetCode

Problem:

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

 

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

 

 

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
       //没什么，分情况而已
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode ln=new ListNode(0);
        if(l1==null&&l2==null) return null;
        else if(l1==null) return l2;
        else if(l2==null) return l1;
        else if(l1.next==null&&l2.next==null){
            ln.val=l1.val+l2.val;
            if(ln.val>9){
                int temp=ln.val%10;
                ln.next=new ListNode(ln.val/10);
                ln.val=temp;
            }
            return ln;
        }
        else if(l1.next==null){
            ln.val=l1.val+l2.val;
            l2.val=0;
            if(ln.val>9){
                int temp=ln.val%10;
                ln.next=new ListNode(ln.val/10);
                ln.val=temp;
            }
            ln.next=addTwoNumbers(ln.next,l2.next);
            return ln;
        }
        else if(l2.next==null){
            ln.val=l1.val+l2.val;
            l1.val=0;
            if(ln.val>9){
                int temp=ln.val%10;
                ln.next=new ListNode(ln.val/10);
                ln.val=temp;
            }
            ln.next=addTwoNumbers(ln.next,l1.next);
            return ln;
        }
        else{
            ln.val=l1.val+l2.val;
            l1.val=0;
            l2.val=0;
            if(ln.val>9){
                int temp=ln.val%10;
                l1.next.val+=ln.val/10;
                ln.val=temp;
            }
            ln.next=addTwoNumbers(l1.next,l2.next);
            return ln;
        }
    }
}