cci-Q2.4 链表的值相加

原文：

You have two numbers represented by a linked list, where each node contains a single digit. The digits are stored in reverse order, such that the 1’s digit is at the head of the list. Write a function that adds the two numbers and returns the sum as a linked list.

EXAMPLE

Input: (3 –> 1 –> 5), (5 –> 9 –> 2)

Output: 8 –> 0 –> 8

译文：

你有两个由单链表表示的数。每个结点代表其中的一位数字。数字的存储是逆序的， 也就是说个位位于链表的表头。写一函数使这两个数相加并返回结果，结果也由链表表示。

例子：(3 –> 1 –> 5), (5 –> 9 –> 2)

输入：8 –> 0 –> 8

使用递归，如果anode和bnode不同时为空，则new一个新的morenode，morenode.data=anode.data+bnode.data+carry(上一次相加的进位)。

 public static void main(String args[]) {        // a = 815        int a[] = {5, 1, 8,};        // b = 3186        int b[] = {6, 8, 1, 3};        LinkedListNode aNode = arrToList(a);        LinkedListNode bNode = arrToList(b);        //output aNode: 518        printList(aNode);        //output bNode 6813        printList(bNode);        LinkedListNode result = add(aNode, bNode, 0);        //output result 1004        printList(result);    }    public static void printList(LinkedListNode a) {        LinkedListNode tmp = a;        while (tmp != null) {            System.out.println(tmp.data);            tmp = tmp.next;        };        System.out.println("");    }    public static LinkedListNode arrToList(int[] a) {        LinkedListNode node = null;        LinkedListNode tmp = null;        for (int i = 0; i < a.length; i++) {            LinkedListNode next = new LinkedListNode(a[i]);            if (i == 0) {                node = tmp = next;                continue;            }            tmp.next = next;            tmp = next;        }        return node;    }    public static LinkedListNode add(LinkedListNode a, LinkedListNode b, int carry) {        if (a == null && b == null) {            return null;        }        LinkedListNode result = new LinkedListNode(carry);        int value = carry;        if (a != null) {            value += a.data;        }        if (b != null) {            value += b.data;        }        result.data = value % 10;        LinkedListNode more = add(a == null ? null : a.next, b == null ? null : b.next, value > 9 ? 1 : 0);        result.next = more;        return result;    }