leetcode:Insert Sort List

/**
 * 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) {
		if(!head||head->next==NULL)
			return head;
		ListNode *pstart=new ListNode(0);//添加一个头指针以方便处理，设所有节点数据大于0
		pstart->next=head;
		ListNode *preCur=head,*cur=head->next;
		while(cur!=NULL)
		{
		    ListNode *prePos=pstart,* pos=pstart->next;
			while(pos->val<cur->val)
			{
				prePos=prePos->next;//prePos指向带插入位置的前方
				pos=pos->next;//pos指向待插入位置的后方
			}
			if(pos!=cur)
			{
				preCur->next=cur->next;
				cur->next=pos;
				prePos->next=cur;
				//preCur不变
				cur=preCur->next;
			}
			else
			{
				preCur=cur;
				cur=cur->next;
			}
		}
		head=pstart->next;
		delete pstart;
		return head;
	}
};

时间复杂度