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/**
 * Definition of ListNode
 * class ListNode {
 * public:
 *     int val;
 *     ListNode *next;
 *     ListNode(int val) {
 *         this->val = val;
 *         this->next = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param head: The first node of linked list.
     * @return: The head of linked list.
     */
    ListNode *insertionSortList(ListNode *head) {
        ListNode *dummy = new ListNode(0);
        ListNode *cur = head;
        while (cur != NULL) {
            ListNode *pre = dummy;
            while (pre->next != NULL && pre->next->val < cur->val) {
                pre = pre->next;
            }
            ListNode *temp = cur->next;
            cur->next = pre->next;
            pre->next = cur;
            cur = temp;
        }

        return dummy->next;
    }
};