<p>You are given the <code>head</code> of a <strong>non-empty</strong> linked list representing a non-negative integer without leading zeroes.</p>

<p>Return <em>the </em><code>head</code><em> of the linked list after <strong>doubling</strong> it</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2023/05/28/example.png" style="width: 401px; height: 81px;" />
<pre>
<strong>Input:</strong> head = [1,8,9]
<strong>Output:</strong> [3,7,8]
<strong>Explanation:</strong> The figure above corresponds to the given linked list which represents the number 189. Hence, the returned linked list represents the number 189 * 2 = 378.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2023/05/28/example2.png" style="width: 401px; height: 81px;" />
<pre>
<strong>Input:</strong> head = [9,9,9]
<strong>Output:</strong> [1,9,9,8]
<strong>Explanation:</strong> The figure above corresponds to the given linked list which represents the number 999. Hence, the returned linked list reprersents the number 999 * 2 = 1998. 
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the list is in the range <code>[1, 10<sup>4</sup>]</code></li>
	<li><font face="monospace"><code>0 &lt;= Node.val &lt;= 9</code></font></li>
	<li>The input is generated such that the list represents a number that does not have leading zeros, except the number <code>0</code> itself.</li>
</ul>

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* reverseLL(ListNode* head) {
        if (head == NULL || head->next == NULL) {
            return head;
        }
        ListNode* newhead = reverseLL(head->next);
        ListNode* front = head->next;
        front->next = head;
        head->next = NULL;
        return newhead;
    }
    ListNode* doubleIt(ListNode* head) {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        ListNode *l1 = head, *l2 = head;
        ListNode* newhead1 = reverseLL(l1);
        ListNode* dummy = new ListNode();
        ListNode* temp = dummy;
        int carry = 0;
        while (newhead1 != nullptr || carry) {
            int sum = 0;
            if (newhead1 != nullptr) {
                sum += 2 * (newhead1->val);
                newhead1 = newhead1->next;
            }
            sum = sum + carry;
            carry = sum / 10;
            ListNode* newnode = new ListNode(sum % 10);
            temp->next = newnode;
            temp = temp->next;
        }
        return reverseLL(dummy->next);
    }
};
97875