<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* doubleIt(ListNode* head) {
        
        ListNode *ptr = head;
        bool car = false;
        int count = 0 , i = 0;

        while(ptr != NULL) {
            count++;
            ptr = ptr->next;
        }
        ptr = head;
        vector<int> carry(count);
        while(ptr != NULL) {
            if(ptr != head) {
                carry[i++] = ((2 * ptr->val) / 10);
            }
            count++;
            ptr = ptr->next;
        }
        ptr = head;
        if(((2 * ptr->val) + carry[0]) / 10 >= 1) {
            ListNode *newn = (ListNode *)malloc(sizeof(struct ListNode));
            newn->val = ((2 * ptr->val) + carry[0]) / 10;
            newn->next = ptr;
            head = newn;
            car = true;
        }
        if(car) {
            ptr = head;
            ptr = ptr->next;
        }
        else {
            ptr = head;
        }
        i = 0;
        while(ptr != NULL) {
            ptr->val = ((ptr->val * 2) + carry[i]) % 10;
            i++;
            ptr = ptr->next;
        }

        return head;
    }
};
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