[LintCode] 链表插入排序

/**
 * 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) {
        // write your code here
        ListNode* new_head = new ListNode(0);
        new_head -> next = head;
        ListNode* pre = new_head;
        ListNode* cur = head;
        while (cur) {
            if (cur -> next && cur -> next -> val < cur -> val) {
                while (pre -> next && pre -> next -> val < cur -> next -> val)
                    pre = pre -> next;
                /* Insert cur -> next after pre. */
                ListNode* temp = pre -> next;
                pre -> next = cur -> next;
                cur -> next = cur -> next -> next;
                pre -> next -> next = temp;
                /* Move pre back to the starting node. */
                pre = new_head;
            }
            else cur = cur -> next;
        }
        ListNode* res = new_head -> next;
        delete new_head;
        return res;
    }
};