Function dfs

javascript/0002-add-two-numbers.js:32–52

(l1, l2, tail, sentinel, carry)

};

const dfs = (l1, l2, tail, sentinel, carry) => {
    const sum = (l1?.val || 0) + (l2?.val || 0) + carry;
    const val = sum % 10;
    carry = Math.floor(sum / 10);

    tail.next = new ListNode(val);
    tail = tail.next;

    l1 = l1?.next || null;
    l2 = l2?.next || null;

    add(
        l1,
        l2,
        tail,
        sentinel,
        carry,
    ); /* Time O(MAX(N, M)) | Space O(MAX(N, M)) */

    return sentinel.next;
};

/**
 * https://leetcode.com/problems/add-two-numbers/