#2 Add Two Numbers

问题：

You are given two non-empty linked lists representing two non-negative integers. 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.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

代码：

package solution;

/**
 * Definition for singly-linked list.
 */
 
class ListNode {
    int val;
    ListNode next;
    ListNode(int val){
        this.val=val;
        this.next=null;
    }
}
public class Solution2 {

    public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode c1 = l1;
        ListNode c2 = l2;
        ListNode sentinel = new ListNode(0);
        ListNode d = sentinel;
        int sum = 0;
        while(c1 != null || c2 != null){
            sum /= 10;
            if(c1 != null){
                sum = sum + c1.val;
                c1 = c1.next;
            }
            if(c2 != null){
                sum = sum + c2.val;
                c2 = c2.next;
            }
            d.next = new ListNode(sum % 10);
            d = d.next;
        }
        if(sum / 10 == 1)
            d.next = new ListNode(1);
        return sentinel.next;
    }
    public static void main(String[] args){
        int[] a = new int[] {2,4,3};
        ListNode blistNode=buildListNode(a);
        int[] b = new int[] {5,6,4};
        ListNode alistNode=buildListNode(b);
        System.out.println(addTwoNumbers(alistNode,blistNode));
    }
    private static ListNode buildListNode(int[] input){
        ListNode first = null,last = null,newNode;
        int num;
        if(input.length>0){
            for(int i=0;i

注：存在类型转换问题懒得弄了