結構_奇前偶後

#include <stdio.h>
#include <stdlib.h>
struct ListNode
{
    int val;
    struct ListNode* next;
};


struct ListNode* oddEvenList(struct ListNode* head);


struct ListNode* oddEvenList(struct ListNode* head)
{
    struct ListNode *ptr;
    ptr = head;
    int arr[1000] = {};
    int count = 0;
    while (ptr != NULL) {
        arr[count] = ptr->val;
        count++;
        ptr=ptr->next;
    }
    int count2 = 0;
    ptr = head;
    while (count2<count) {
        ptr->val = arr[count2];
        count2 = count2 + 2;
        ptr = ptr->next;
    }
    count2 = 1;
    while (ptr!=NULL) {
        ptr->val = arr[count2];
        count2 = count2 + 2;
        ptr = ptr->next;
    }
    return head;
}

void Construct(struct ListNode* node, int length, int num)
{
    int a;
    scanf("%d", &a);
    node->val = a;

    if (num >= length)
    {
        node->next = NULL;
        return;
    }
    node->next = (struct ListNode*)malloc(sizeof(struct ListNode));
    num++;
    Construct(node->next, length, num);
}

int main()
{
    struct ListNode* head;
    int n, a, length;
    head = (struct ListNode*)malloc(sizeof(struct ListNode));
    scanf("%d", &n);
    while (n--)
    {
        scanf("%d", &length);
        Construct(head, length, 1);
        struct ListNode* ans = oddEvenList(head);
        struct ListNode* ptr;

        ptr = ans;

        while (ptr != NULL)
        {
            printf("%d ", ptr->val);
            ptr = ptr->next;
        }
        printf("\n");
    }
}