Leetcode 题目解析之 Add Two Numbers

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

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        if (l1 == null && l2 == null) {
            return null;
        }

        if (l1 == null) {
            return l2;
        }

        if (l2 == null) {
            return l1;
        }

        ListNode p1 = l1;
        ListNode p2 = l2;

        int carry = 0;

        ListNode head = new ListNode(0);
        ListNode result = head;

        while (carry != 0 || p1 != null || p2 != null) {

            int v1 = 0;
            if (p1 != null) {
                v1 = p1.val;
                p1 = p1.next;
            }

            int v2 = 0;
            if (p2 != null) {
                v2 = p2.val;
                p2 = p2.next;
            }

            int tmp = v1 + v2 + carry;
            carry = tmp / 10;
            head.next = new ListNode(tmp % 10);
            head = head.next;
        }

        return result.next;
    }