，。为什么会不通过？

Question

注释如图，为什么没有通过。？感觉没有什么别的情况，应该是没有了。

Answer 1

修改如下：

#include <stdio.h>
#include <stdlib.h>
struct cell
{
    int x;
    struct cell* next;
};
struct cell* build(void)
{
    struct cell* head, * p, * tmp;
    int n;
    head = tmp = p = NULL;
    scanf("%d", &n);
    while (n != 0)
    {
        p = (struct cell*)malloc(sizeof(struct cell));
        p->next = NULL;
        p->x = n;
        if (head == NULL)
        {
            head = p;
            tmp = p;
        }
        else
        {
            tmp->next = p;
            tmp = p;
        }
            
        scanf("%d", &n);
    }
    return head;
}

void print(struct cell* head)
{
    if (head != NULL)
    {
        printf("%d", head->x);
        print(head->next);
    }
        
}

void release(struct cell* head)
{
    struct cell* t;
    if (head != NULL)
    {
        t = head->next;
        free(head);
        release(t);
    }
}

int main(void)
{
    struct cell* head;
    head = build();
    if (head != NULL)
        print(head);
    else
        printf("NULL");
    release(head);
    return 0;
}