Insertion Sort List

Sort a linked list using insertion sort.

指针的初始值设置有问题，梁旭两天童颜的错误了。

/**
 * 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 * guide = new ListNode(0);
        guide->next = head;
        ListNode * temp = head->next;
        ListNode * temp_pre = head;
        while(temp != NULL)
        {
            int temp_val = temp->val;
            ListNode * p = guide->next;
            ListNode * p_pre = guide;
            while(temp_val > p->val && p != temp)
            {
                p = p->next;
                p_pre =p_pre->next;
            }
            if(p == temp)
            {
                temp =temp->next;
                temp_pre = temp_pre->next;
                continue;
            }
            else
            {
                temp_pre ->next =temp->next;
                p_pre->next =temp;
                temp->next = p;
                temp = temp_pre->next;
                //return guide->next;
            }
            
        }
        return guide->next;

        
    }
};