Sort a linked list using insertion sort.

class Solution {

public:

    ListNode *insertionSortList(ListNode *head) {

        if(head == NULL || head->next == NULL)

            return head;

        ListNode *result;

        result->val = INT_MIN;

        result->next = NULL;

        ListNode *cur=head,*pos,*pre;

        while(cur!=NULL)

        {

            pos = result->next;

            pre = result;

            while(pos != NULL && pos->val <= cur->val)

            {

                pre = pos;

                pos = pos->next;

            }

            ListNode *temp = cur->next;

            pre->next = cur;

            cur->next = pos;

            cur = temp;

        }

        return result->next;

    }

};