LeetCode147. 对链表进行插入排序

我的代码：

class Solution {
public:
    ListNode* insertionSortList(ListNode* head) {
        if (!head || !head->next) return head;
        ListNode *res = head;
        ListNode *p1 = res;
        ListNode *pcur = head->next;
        ListNode *ppre = NULL; //已排序链表的ppre
        ListNode *pnext = NULL;
        res->next = NULL;//先将链表断开，分为待插入和已排序两部分
        while (pcur) {
            pnext = pcur->next;
            
            ppre = NULL;
            p1 = res;
            while (p1 && p1->val < pcur->val) {
                ppre = p1;
                p1 = p1->next;
            }
            
            //如果比已排序链表中所有元素都大，则尾插
            if (p1 == NULL) {
                ppre->next = pcur;
                pcur->next = NULL;
            }
            //比已排序链表头结点都小，头插
            else if (ppre == NULL) {
                pcur->next = res;
                res = pcur;
            }
            //如果在中间某处找到位置，则插入
            else if (p1->val >= pcur->val) {
                pcur->next = p1;
                ppre->next = pcur;
            }
            
            pcur = pnext;
        }
        return res;
    }
};

LeetCode官方题解代码：

class Solution {
public:
    ListNode* insertionSortList(ListNode* head) {
        if (!head || !head->next) return head;
        ListNode *dummyHead = new ListNode(0);
        dummyHead->next = head;
        ListNode *lastSorted = head, *pcur = head->next;
        
        while (pcur) {
            if (lastSorted->val <= pcur->val) {
                lastSorted = lastSorted->next;
            }
            else {
                ListNode *prev = dummyHead;
                while (prev->next->val <= pcur->val) {
                    prev = prev->next;
                }
                lastSorted->next = pcur->next;
                //头插
                pcur->next = prev->next;
                prev->next = pcur;
            }
            pcur = lastSorted->next;
        }
        return dummyHead->next;
    }
};

可以看出，我的代码有很多冗余的指针，且判断分支较多，不易读，官方代码就使用了三个指针，非常简洁。