[lintcode easy]Add Two Numbers

Add Two Numbers

 

You have two numbers represented by a linked list, where each node contains a single digit. The digits are stored in reverse order, such that the 1's digit is at the head of the list. Write a function that adds the two numbers and returns the sum as a linked list.

 

 

Example

Given 7->1->6 + 5->9->2. That is, 617 + 295.

Return 2->1->9. That is 912.

Given 3->1->5 and 5->9->2, return 8->0->8.

 

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;      
 *     }
 * }
 */
public class Solution {
    /**
     * @param l1: the first list
     * @param l2: the second list
     * @return: the sum list of l1 and l2 
     */
    public ListNode addLists(ListNode l1, ListNode l2) {
        
        // write your code here
        if(l1==null && l2==null) return null;
        ListNode sumhead=new ListNode(0);
        ListNode s1=sumhead;
        int sum=0;while(l1!=null && l2!=null)
        {
            sum=l1.val+l2.val+sum/10;
            l1=l1.next;
            l2=l2.next;
            s1.next=new ListNode(sum%10);
            s1=s1.next;
        }
        while(l1!=null)
        {
            sum=l1.val+sum/10;
            l1=l1.next;
            s1.next=new ListNode(sum%10);
            s1=s1.next;
        }
        while(l2!=null)
        {
            sum=l2.val+sum/10;
            l2=l2.next;
            s1.next=new ListNode(sum%10);
            s1=s1.next;
        }
        if(sum/10 !=0)
        {
                 s1.next=new ListNode(sum/10);
        }
       return sumhead.next;
    }
}