<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>

class Solution {
    ListNode* solve(vector<int>&res){
        if(res.empty()){
            return NULL;
        }
        ListNode* head = new ListNode(res[0]);
        ListNode*temp = head;
        for(int i  = 1; i< res.size(); i++){
            temp -> next = new ListNode(res[i]);
            temp = temp->next;
        }
        return head;
    }
public:
    ListNode* doubleIt(ListNode* head) {
        vector<int>res;
        ListNode* temp = head;
        while(temp!= NULL){
          res.push_back(temp->val);
          temp = temp->next;
        }
        int carry = 0;
        for(int i = res.size()-1; i>=0 ; i--){
            int doublet = 2* res[i] + carry;
            res[i]=doublet % 10;
            carry = doublet/10;
        }
            if(carry > 0) {
            res.insert(res.begin(), carry);
          }
        return solve(res);
    }
};
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