Почему LeetCode не принимает код?

Question

[MeMoJlor]

Все работает, код выполняет необходимые функции, но выходит Runtime Error
Код:

spoiler

const addTwoNumbers = (l1, l2) => {
  let res = [],
  max = Math.max(l1.length, l2.length),
  sum = [],
  bool = false;
  for (let i = 1; i <= max; i++) {
    const digit = (l1[l1.length - i] | 0) + (l2[l2.length - i] | 0) + bool;
    bool = digit > 9;
    res.unshift(digit % 10);
  }
  if (bool) {
    res.unshift(1);
  }
  for(let i = res.length - 1; i >= 0; i--) {
    sum.push(res[i])
  }
  return sum;
};
console.log(addTwoNumbers([9,9,9,9], [9,9,9]));

Ошибка:

Line 36 in solution.js
             throw new TypeError(__serialize__(ret) + " is not valid value for the expected return type ListNode");
             ^
TypeError: [] is not valid value for the expected return type ListNode
    Line 36: Char 20 in solution.js (Object.<anonymous>)
    Line 16: Char 8 in runner.js (Object.runner)
    Line 20: Char 26 in solution.js (Object.<anonymous>)
    Line 1251: Char 30 in loader.js (Module._compile)
    Line 1272: Char 10 in loader.js (Object.Module._extensions..js)
    Line 1100: Char 32 in loader.js (Module.load)
    Line 962: Char 14 in loader.js (Function.Module._load)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
    Line 17: Char 47 in run_main_module.js

Что это означает?

Answer 1

[Александр Аксентьев]

Потому что массив это не ListNode.

Надо вернуть связный список

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function(l1, l2) {
    var dummy = {
      val : -1,
      next : null
    };
    var curr = dummy;
    while (l1 && l2) {
        if (l1.val > l2.val) {
            curr.next = l2;
            l2 = l2.next;
        } else {
            curr.next = l1;
            l1 = l1.next;
        }
        curr = curr.next;
    }
    
    curr.next = l1 || l2;

    return dummy.next;
};

https://stackoverflow.com/a/62864715/1603055