LeetCode - Add Two Numbers

题目：

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

思路：

就像做加法一样，记得进位和判断结尾

package list;

public class AddTwoNumbers {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode p = new ListNode(0);
        ListNode node = p;
        int sum = 0;
        int carry = 0;
        while (true) {
            if (l1 != null && l2 != null) {
                sum = l1.val + l2.val + carry;
                l1 = l1.next;
                l2 = l2.next;
            } else if (l1 != null) {
                sum = l1.val + carry;
                l1 = l1.next;
            } else if (l2 != null){
                sum = l2.val + carry;
                l2 = l2.next;
            } else {
                sum = carry;
                if (sum == 0)
                    break;
            }
            
            p.next = new ListNode(sum % 10);
            carry = sum / 10;
            p = p.next;
        }
        
        return node.next;
    }
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub

    }

}