Insertion Sort List

Sort a linked list using insertion sort.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *insertionSortList(ListNode *head) {
        ListNode dummy(INT_MIN);
        dummy.next = head;
        ListNode* cur = &dummy;
        while(cur->next) {
            if(cur->next->val >= cur->val)
                cur = cur->next;
            else 
                insert(&dummy, cur, cur->next);
        }
        return dummy.next;
    }
    
    void insert(ListNode* head, ListNode* tail, ListNode* node) 
    {
        ListNode* cur = head;
        while(cur->next->val <= node->val && cur != tail) {
            cur = cur->next;
        }
        tail->next = node->next;
        node->next = cur->next;
        cur->next = node;
    }
};