[leetcode] 147. Insertion Sort List 解题报告

题目链接：https://leetcode.com/problems/insertion-sort-list/

Sort a linked list using insertion sort.

思路：我发现自从用了虚拟头结点之后刷链表简直是毫无阻碍，哈哈！！


代码如下：

/**
* 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* pHead = new ListNode(0);//创建虚拟头节点
pHead->next = head;
ListNode *p = head->next;
head->next = NULL;
while(p)
{
ListNode *q = p->next, *k = pHead;
while(k->next && k->next->val < p->val)//查找要插入的位置
k = k->next;
p->next = k->next;
k->next = p;
p = q;
}
head = pHead->next;
delete pHead;
return head;
}
};