2. 两数相加

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode head = new ListNode(0);
        ListNode ln = head;
        ListNode ln1 = l1;
        ListNode ln2 = l2;
        int temp = 0;
        while (ln1 != null || ln2 != null) {
            if (ln1 == null) {
                ln.next = new ListNode((ln2.val + temp) % 10);
                temp = (ln2.val + temp) / 10;
                 ln = ln.next;
                ln2 = ln2.next;
            }
            else if(ln2 == null) {
                ln.next = new ListNode((ln1.val + temp) % 10);
                temp = (ln1.val + temp) / 10;
                 ln = ln.next;
                ln1 = ln1.next;
            }
            else {
                ln.next = new ListNode((ln1.val+ln2.val + temp) % 10);
                temp = (ln1.val + ln2.val+ temp) / 10;
                 ln = ln.next;
                ln1 = ln1.next;
            ln2 = ln2.next;
            }

        }if(temp!=0)
            ln.next = new ListNode(1);
        return head.next;
    }
}2. 两数相加