单链表的插入排序

/**
 * 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) {
            ListNode *list = head;

    if (list == NULL || list->next == NULL)
    {
        return list;
    }

    ListNode *p1 = list;
    ListNode *p2 = p1->next;
    ListNode *p3 = p2->next;

    if (p1->val > p2->val)
    {
        swap(p1->val, p2->val);
    }

    while (p3 != NULL)
    {
        ListNode *temp = p3->next;

        if (p1->val > p3->val)
        {
            ListNode *tmp = p3;
            while (p2->next != p3)
                p2 = p2->next;
            p2->next = p3->next;
            tmp->next = p1;
            list=tmp;
            p1 = list;
            p2 = p1->next;
            p3 = temp;
        }
        else
        {
            while (p2->val < p3->val)
            {
                p1 = p1->next;
                p2 = p2->next;
            }
            if (p2 != p3)
            {
                    p1->next = p3;
                    ListNode *tmp = p2;
                    while (tmp->next != p3)
                        tmp = tmp->next;
                    tmp->next = p3->next;
                    p3->next = p2;
                    p1 = list;
                    p2 = list->next;
                    p3 = temp;
            }
            else
            {
                    p1 = list;
                    p2 = list->next;
                    p3 = temp;
            }
            
        }
        
    }
    return list;
        
    }
};