c - 在 C 中使用 typedef 和指针来实现堆栈

Question

我在编译这段代码时遇到问题，因为我不知道如何使用 typedef (但我们必须这样做)。我的方法 Push 将 item *elem 作为输入，但 top -> info = *elem 不起作用。这是我的代码:

#include <stdio.h>
#include <stdlib.h>



struct node  
{
int info;

struct node *ptr;
}*top,*top1,*temp;


typedef struct item {

} item;

// my methods
void push(item *elem);
void *pop();
void empty();
void create();

int count = 0;

void create()
{
   top = NULL;
 }


 // pushing the elements in the stack
 void push(item *elem)
 {
    if (top == NULL)
    {
        top =(struct node *)malloc(1*sizeof(struct node));
        top->ptr = NULL;
        top->info = *elem;
    }
   else
    {
        temp =(struct node *)malloc(1*sizeof(struct node));
        temp->ptr = top;
        temp->info = *elem;  // here is the error "not compatible"
        top = temp;
    }
    count++;
 }
    // I also got this, this is for creating a new elem, but I do not  
     // know how to implement this method
  item* new_item(int value) {

 }

Answer 1

首先，typedef:

struct node  
{
    int info;
    struct node *ptr;
};
typedef struct node item;

并创建一个指针:

item *top = NULL;

push 应该简单地将元素插入堆栈顶部。

void push(item *elem)
{
    // I assume elem is already created.
    if (top == NULL)
    {
        top = elem;
    }
    else
    {
        top->ptr = elem;
        top = elem;
    }
    count++;
}

new_item 应分配内存并初始化

item* new_item(int value)
{
    item *temp = malloc(sizeof(item));
    item->info = value;
    item->ptr = NULL;
}

在其他地方，创建并添加......

item *someNewItem = new_item(100);
push(someNewItem);
// Later on, someNewItem needs to be free()'d