[Leet code 2]Two Sum

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode headNode = new ListNode(0);
        ListNode p = headNode;
        int carry = 0;
        
        while (l1 != null && l2 != null) {
            int var = l1.val + l2.val + carry;
            carry = var / 10;
            var = var % 10;
            
            ListNode node = new ListNode(var);
            
            p.next = node;
            p = p.next;
            
            l1 = l1.next;
            l2 = l2.next;
            
        }
        //要考虑到前面可能有进位，要加上carry
        while (l1 != null) {
            int var = l1.val + carry;
            carry = var /10;
            var = var % 10;
            ListNode node = new ListNode(var);
            p.next = node;
            p = p.next;
            l1 = l1.next;
        }
        
        while (l2 != null) {
            int var = l2.val + carry;
            carry = var /10;
            var = var % 10;
            ListNode node = new ListNode(var);
            p.next = node;
            p = p.next;
            l2 = l2.next;
        }
        //要考虑到最后有个进位，就新建一个节点
        if (carry != 0) {
            ListNode node = new ListNode(carry);
            p.next = node;
            p = p.next;
        }
        return headNode.next;
    }
}