Insertion Sort List

Sort a linked list using insertion sort

链表的插入排序

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 *cur = head->next;
		head->next = NULL;
		while(cur != NULL){
			ListNode *next = cur->next;
			if(cur->val < head->val){
				cur->next=head;
				head = cur;
			}
			else{
				ListNode * pre = head, *post = head->next;
				while(post && cur->val > post->val ){
					pre = post;
					post = post->next;
				}
				pre->next = cur;
				cur->next = post;
			}
			cur = next;
		}
    return head;
	}
};

刚开始老是报错，结果发现我把判空操作跟val值比较大小的顺序搞颠倒了...不确保非空怎么能比较值了...又脑残了一把