C语言单链表实现栈

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

typedef struct NODE
{
    int val;
    struct NODE *next;
}node;//define node

node * head=NULL;//init head_node of stack

//create node
node *create_node(int val)
{
    node *p=(node *)malloc(sizeof(node));
    p->val=val;
    p->next=NULL;
    return p;
}

//push 头插法
node *push(int val)
{
    node *p=create_node(val);
    p->next=head;
    head=p;
    return head;
}

//peek
int peek(node *link)
{
    if(length_stack(link)==0)
    {
        printf("此栈为空");
        return 0;
    }
    return head->val;
}

//calculate length_length
int length_stack(node *link)
{
    int count=0;
    while(link)
    {
        count++;
        link=link->next;
    }
    return count;
}


//pop
int pop(node *link)
{
    node *p;
    p=head;
    head=head->next;
    free(p);
    return p->val;
}
//printf_stack
void print_stack()
{
    while(head)
    {
        printf("%d   ",head->val);
        head=head->next;
    }
}


int main()
{
    push(1);
    push(2);
    push(3);
    push(4);
    push(5);
    peek(head);
    int size=length_stack(head);
    printf("栈长度为：%d\n",size);

    print_stack();

}