<p>Given the <code>head</code> of a linked list, return <em>the list after sorting it in <strong>ascending order</strong></em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/09/14/sort_list_1.jpg" style="width: 450px; height: 194px;" />
<pre>
<strong>Input:</strong> head = [4,2,1,3]
<strong>Output:</strong> [1,2,3,4]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/09/14/sort_list_2.jpg" style="width: 550px; height: 184px;" />
<pre>
<strong>Input:</strong> head = [-1,5,3,4,0]
<strong>Output:</strong> [-1,0,3,4,5]
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> head = []
<strong>Output:</strong> []
</pre>

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

<ul>
	<li>The number of nodes in the list is in the range <code>[0, 5 * 10<sup>4</sup>]</code>.</li>
	<li><code>-10<sup>5</sup> &lt;= Node.val &lt;= 10<sup>5</sup></code></li>
</ul>

<p>&nbsp;</p>
<p><strong>Follow up:</strong> Can you sort the linked list in <code>O(n logn)</code> time and <code>O(1)</code> memory (i.e. constant space)?</p>

/**
 * 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* sortedList(ListNode* &head1,vector<int> v)
{
    int count = 0;
    ListNode* temp = head1;
    while(count != v.size())
    {
        temp -> next = new ListNode(v[count++]);
        temp = temp -> next;
    }
    return head1->next;
}
    ListNode* sortList(ListNode* head) {
        ListNode* temp = head;
        vector<int> v;
        while(temp != NULL)
        {
            v.push_back(temp -> val);
            temp = temp -> next; 
        }
        sort(v.begin(),v.end());

        ListNode* dummy = new ListNode(0);
        ListNode* head1 = dummy;

        ListNode* ans = sortedList(head1,v);
        return ans;
    }
};




// ListNode* curr1 = list1;
//         ListNode* curr2 = list2;

//         ListNode ans = new ListNode;

//         while(curr1 != NULL && curr2 != NULL)
//         {
//             if(curr1 -> val <= curr2 -> val)
//             {
//                 ans -> next = curr1;
//                 curr1 = curr1 -> next;
//             }
//             else{
//                 ans -> next = curr2;
//                 curr2 = curr2 -> next;
//             }
//             ans = ans -> next;
//         }
//         if(curr1 == NULL)
//         {
//             ans -> next = curr2;
//         }
//         else if(curr2 == NULL)
//         {
//             ans -> next = curr1;
//         }
//         return ans;
66321