2. 两数相加(2019-01-12)

class Solution {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        int carry = 0;

        ListNode temp = new ListNode(0);

        ListNode result = temp;

        while (l1 != null || l2 != null) {

            int sum = (l1 != null? l1.val: 0) + (l2 != null? l2.val: 0) + carry;

            carry = sum / 10; temp.next = new ListNode(sum % 10);

            l1 = l1 != null? l1.next: l1;

            l2 = l2 != null? l2.next: l2;

            temp = temp.next;

        }

        if (carry > 0) {

            temp.next = new ListNode(carry);

        }

        return result.next;

    }

}