[LeetCode] 2. Add Two Numbers (JAVA)

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 contains a single digit. Add the two numbers and return the sum as a linked list.

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

Example 1:

Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.

Example 2:

Input: l1 = [0], l2 = [0]
Output: [0]

Example 3:

Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
Output: [8,9,9,9,0,0,0,1]

Constraints:

The number of nodes in each linked list is in the range [1, 100].
0 <= Node.val <= 9
It is guaranteed that the list represents a number that does not have leading zeros.

My Code

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        if(l2==null) return l1;
        int sum = (l1==null?0:l1.val)+l2.val;
        if(sum>=10) {
            sum %= 10;
            if(l2.next==null) {
                l2.next = new ListNode(1);
            } else {
                l2.next.val += 1;
            }
        }
        l2.val = sum;
        l2.next = addTwoNumbers(l1==null?l1:l1.next, l2.next);
        return l2;
    }
}

Submission Detail

Runtime: 1 ms
Memory Usage: 39.4 MB

Comment

Using Recursive