LeetCode 2. Add Two Numbers

2. Add Two Numbers

Question

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.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

 Solution

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int num1 = 0;
        int num2 = 0;
        int ret = 0;
        ListNode head = new ListNode(0);
        ListNode temp = head;
        while (l1!=null&&l2!=null){
            num1 = l1.val;
            num2 = l2.val;
            temp.next=new ListNode ((num1+num2+ret)%10);
            ret = (num1+num2+ret)/10;
            temp = temp.next;
            l1 = l1.next;
            l2 = l2.next;

        }

        if (l1==null&& l2!=null){

            while (l2!=null){
                num2 = l2.val;
                temp.next=new ListNode ((num2+ret)%10);
                ret = (num2+ret)/10;
                temp = temp.next;
                l2 = l2.next;
            }
        }
        if (l1!=null&& l2==null){

            while (l1!=null){
                num1 = l1.val;
                temp.next=new ListNode ((num1+ret)%10);
                ret = (num1+ret)/10;
                temp = temp.next;
                l1 = l1.next;
            }
        }

        if (ret>0){
            temp.next = new ListNode(ret);  //别忘了
        }

        return head.next;
    }
}