Interview - Add two number - #2

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

题目比较简单, 主要考察链表操作的熟练程度, 以及各种边界情况的处理, 这种题目, 要一次写对, 不留 bug.

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        if (l1 == null) return l2;
        if (l2 == null) return l1;
        
        ListNode head = new ListNode(0);
        ListNode curr = head;
        boolean isCarry = false;
        while (l1 != null || l2 != null) {
            int val = (isCarry ? 1 : 0) + (l1 == null ? 0 : l1.val) + (l2 == null ? 0 : l2.val);
            if (val >= 10) {
                isCarry = true;
                val -= 10;
            } else {
                isCarry = false;
            }
            ListNode node = new ListNode(val);
            curr.next = node;
            curr = node;
            l1 = l1 == null ? null : l1.next;
            l2 = l2 == null ? null : l2.next;
        }
        
        if (isCarry) {
            ListNode node = new ListNode(1);
            curr.next = node;
        }
        
        return head.next;
    }