LeetCode Add Two Numbers

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

/**
 * 模拟2个大数相加
 * Created by lezg on 16/4/6.
 */
public class Solution {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode prev = new ListNode(0);
        ListNode head = prev;
        int carry = 0;
        while (l1 != null || l2 != null) {
            ListNode curr = new ListNode(0);
            int sum = 0;
            if (l1 != null) {
                sum += l1.val;
                l1 = l1.next;
            }
            if (l2 != null) {
                sum += l2.val;
                l2 = l2.next;
            }
            sum += carry;
            curr.val = sum % 10;
            carry = sum / 10;
            prev.next = curr;
            prev = curr;
        }
        if (carry == 1) {
            ListNode curr = new ListNode(0);
            curr.val = carry;
            prev.next = curr;
        }
        return head.next;
    }

}