为什么运行不了，链表反向数组输出

Question

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */


/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* reversePrint(struct ListNode* head, int* returnSize){
int length=1;
struct ListNode* pre=NULL;
struct ListNode* cur=head;
while(cur){
struct ListNode* next=cur->next;
cur->next=pre;
pre=cur;
cur=next;
length++;
}
    int* arr=(int*)malloc(sizeof(int)*length);
for(int i=0;i<length;i++){
    if(pre==NULL){
        break;
    }
    arr[i]=pre->val;
    pre=pre->next;
}
return arr;
}

Answer 1

int* reversePrint(struct ListNode* head, int* returnSize) {
    int length = 0;
    struct ListNode* pre = NULL;
    struct ListNode* cur = head;

    while (cur) {
        struct ListNode* next = cur->next;
        cur->next = pre;
        pre = cur;
        cur = next;
        length++;
    }

    *returnSize = length;
    int* arr = (int*)malloc(sizeof(int) * (length - 1));

    for (int i = 0; i < length; i++) {
        if (pre == NULL) {
            break;
        }
        arr[i] = pre->val;
        pre = pre->next;
    }

    return arr;
}