C语言， 反转链表，直接反转

#include 
#include 
 
 
 struct ListNode {
     int val;
     struct ListNode *next;
 };
 
 struct ListNode* init(int val){
     struct ListNode* head = malloc(sizeof(struct ListNode));
     head->next = NULL;
     head->val = val;
     return head;
 }
 
 void insert(struct ListNode* head, int val){
     struct ListNode* p = head;
     while(p->next){
         p = p->next;
     }
     
     struct ListNode* node = malloc(sizeof(struct ListNode));
     node->next = NULL;
     node->val = val;
     p->next = node;
     
 }
 
void print(struct ListNode* head){
    struct ListNode* p = head;
    while(p){
        printf("%d ", p->val);
        p = p->next;
    }
}


struct ListNode* reverseList(struct ListNode* head){

    if (head == NULL){
        return head;
    }
    struct ListNode* p = head;
    struct ListNode* pre = head;
    if (pre->next== NULL){
        return pre;
    }
    struct ListNode* cur = pre->next;
    if (cur->next == NULL){
        cur->next = pre;
        pre->next = NULL;
        return cur;
    }
    struct ListNode* next = cur->next;

    pre->next = NULL;
    cur->next = pre;

    while(next->next){
        pre = cur;
        cur = next;
        next = next->next;
        cur->next = pre;
    }

    next->next = cur;
    return next;

}
 
int main()
{
    struct ListNode* head = init(1);
    insert(head,2);
    insert(head,3);
    insert(head,4);
    insert(head,5);
    insert(head,6);
    insert(head,7);
    insert(head,8);
    insert(head,9);
    insert(head,10);
    print(head);
    printf("n");
    struct ListNode* re = reverseList(head);
    print(re);
    return 0;
}