Poison

2. Add Two Numbers

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class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int carry = 0;
        ListNode dummyHead = new ListNode(0);
        ListNode curr = dummyHead;
        while (carry != 0 || l1 != null || l2 != null) {
            int sum = carry;
            if (l1 != null) {
                sum += l1.val;
                l1 = l1.next;
            }
            if (l2 != null) {
                sum += l2.val;
                l2 = l2.next;
            }

            int value = sum % 10;
            carry = sum / 10;

            curr.next = new ListNode(value);
            curr = curr.next;
        }

        return dummyHead.next;
    }
}

可以把最后一次的进位放在 while 里面处理，能够减少重复代码。

Reference

2. Add Two Numbers