[leetcode] Insertion 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) return head;
ListNode *index, *cur=head->next, *p, *pre;
ListNode *phead = new ListNode(0);
phead->next = head;
head->next = NULL;
while(cur) {
int val = cur->val;
pre = phead;
index = pre->next;
p = cur->next;
while(index && index->val<=val) {
pre=index;
index=index->next;
}
cur->next = index;
pre->next = cur;
cur = p;
}
head = phead->next;
delete phead;
return head;
}
};