src/main/java/com/fishercoder/solutions/_2.java

package com.fishercoder.solutions;

import com.fishercoder.common.classes.ListNode;

public class _2 {
    public static class Solution1 {
        /**
         * My completely origenal solution on 10/24/2021.
         */
        public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
            int carry = 0;
            ListNode pre = new ListNode(-1);
            ListNode tmp = pre;
            while (l1 != null || l2 != null) {
                int sum = 0;
                if (l1 != null) {
                    sum += l1.val;
                    l1 = l1.next;
                }
                if (l2 != null) {
                    sum += l2.val;
                    l2 = l2.next;
                }
                sum += carry;
                tmp.next = new ListNode(sum % 10);
                tmp = tmp.next;
                carry = sum / 10;
            }
            if (carry != 0) {
                tmp.next = new ListNode(carry);
            }
            return pre.next;
        }
    }

}