leetcode/2. Add Two Numbers/Solution.java

/**
 * 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) {
      ListNode dummy = new ListNode();
      var cur = dummy;

      int carry = 0;

      while (carry != 0 || l1 != null || l2 != null) {
        int v1 = (l1 != null) ? l1.val : 0;
        int v2 = (l2 != null) ? l2.val : 0;

        int val = v1 + v2 + carry;
        carry = val / 10;
        val = val % 10;

        cur.next = new ListNode(val);

        cur = cur.next;

        l1 = (l1 != null) ? l1.next : null;
        l2 = (l2 != null) ? l2.next : null;
      }

      return dummy.next;
    }
}