/**
 * 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:
    struct compare {
        bool operator()(ListNode* a, ListNode* b) {
            return a->val < b->val;
        }
    };
    ListNode* sortList(ListNode* head) {
        vector<ListNode*> vec;
        while (head) {
            vec.push_back(head);
            head = head->next;
        }
        sort(vec.begin(), vec.end(), compare());
        ListNode* res = new ListNode();
        ListNode* temp = res;
        for (int i = 0; i < vec.size(); i++) {
            res->next = vec[i];
            res = res->next;
        }
        return temp->next;
    }
};