[LeetCode Javascript]2 - Add Two Numbers

Problem

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]

Solution

Shamefully, I thought, ‘Wow, is there a “ListNode” type in javascript? that’s new to me.’ And I tried to submit my solution and got an error message.

And turns out, ListNode is just a function they made. And here’s the definition:

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**

I missed this comment, so I had no idea, so I had to refer to other people’s correct answers.

https://leetcode.com/problems/add-two-numbers/solutions/1020/javascript-solution/

I tried to submit my own solution, but I ended up writing code almost the same as the above solution.

Anyway, my solution(which is already the perfect solution because I referred to the best solution) is this:

let addTwoNumbers = function (l1, l2) {
  let sum = 0;
  const answer = new ListNode(0);
  let current = answer;

  while (l1 || l2 || sum > 0) {
    if (l1) {
      sum += l1.val;
      l1 = l1.next;
    }
    if (l2) {
      sum += l2.val;
      l2 = l2.next;
    }
    if (sum >= 10) {
      current.next = new ListNode(sum - 10);
      current = current.next;
      sum = 1;
    } else {
      current.next = new ListNode(sum);
      current = current.next;
      sum = 0;
    }
  }

  return answer.next;
};