leetcode[147]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) {
        if(head==NULL||head->next==NULL)return head;
        ListNode *newh=new ListNode(0);
        ListNode *p=head;
        while(p)
        {
            ListNode *pretmp=newh;
            ListNode *pnext=p->next;
            ListNode *tmp=newh->next;
            if(!tmp)
            {
                newh->next=p;
                newh->next->next=NULL;
                p=pnext;
                continue;
            }
            while(tmp)
            {
                if(p->val<=tmp->val)
                {
                    pretmp->next=p;
                    p->next=tmp;
                    break;
                }
                else
                {
                    pretmp=tmp;
                    tmp=tmp->next;
                }
            }
            if(!tmp)
            {
                pretmp->next=p;
                pretmp->next->next=NULL;
            }
            p=pnext;
        }
        return newh->next;
    }
};