LeetCode题解：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

题意：两个链表各自代表一个正整数，求它们的和

解题思路：加法运算

代码：

public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode result = new ListNode(0);
        ListNode head = result;

        int sum = 0;
        while(l1 != null || l2 != null){
            sum /= 10;

            if(l1 != null){
                sum += l1.val;
                l1 = l1.next;
            }

            if(l2 != null){
                sum += l2.val;
                l2 = l2.next;
            }

            head.next = new ListNode(sum % 10);
            head = head.next;
        }

        if(sum / 10 == 1){
            head.next = new ListNode(1);
        }

        return result.next;
    }
}