链栈

链栈

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

typedef struct Node
{
    int data;
    struct Node * pNext;
}NODE, *PNODE;

typedef struct Stack
{
    PNODE pTop;   //top指针
    PNODE pBottom;    //bottom指针
}STACK, *PSTACK;

void init(PSTACK);
void push(PSTACK,int);
void traverse(PSTACK);
bool is_empty(PSTACK);
bool pop(PSTACK,int*);
void clear(PSTACK);

int main()
{
    STACK S;  //STACK 等价于struct Stack
    int val;

    init(&S);   //目的是造出一个空栈
    printf("入栈元素是");
    push(&S,1);   //压栈
    push(&S,2);
    push(&S,3);
    push(&S,4);
    push(&S,5);
    traverse(&S);  //遍历输出

    if( pop(&S,&val) )
    {
        printf("出栈成功，出栈的元素是%d ",val);
    }
    else
    {
        printf("出栈失败!
");
    }
    traverse(&S);  //遍历输出

    clear(&S);
    traverse(&S);  
    return 0;
}

void init(PSTACK pS)
{
    pS->pTop = (PNODE)malloc(sizeof(NODE));
    if(NULL == pS->pTop)
    {
        printf("动态内存分配失败");
        exit(-1);
    }
    else
    {
        pS->pBottom = pS->pTop;
        pS->pTop->pNext = NULL;  //pS->Bottom->pNext = NULL;
    }
}

void push(PSTACK pS,int val)
{
    PNODE pNew = (PNODE)malloc(sizeof(NODE));

    pNew->data = val;
    pNew->pNext = pS->pTop;  //pS->ptop能改成pS->pBottom
    pS->pTop = pNew;
    return;
}

void traverse(PSTACK pS)
{
    PNODE p = pS->pTop;

    while(p != pS->pBottom)
    {
        printf("%d ",p->data);
        p = p->pNext;
    }
    printf("
");
    return;
}

bool is_empty(PSTACK pS)
{
    if(pS->pTop == pS->pBottom)
        return true;
    else
        return false;
}

bool pop(PSTACK pS,int *pVal)
{
    if( is_empty(pS) )
    {
        return false;
    }
    else
    {
        PNODE r = pS->pTop;
        *pVal = r->data;
        pS->pTop = r->pNext;
        free(r);
        r = NULL;
        return true;
    }
}

void clear(PSTACK pS)
{
    if( is_empty(pS) )
    {
        return;
    }
    else
    {
        PNODE p = pS->pTop;
        PNODE q = NULL;

        while(p != pS->pBottom)
        {
            q = p->pNext;
            free(p);
            p = q;
        }
        pS->pTop = pS->pBottom;
    }
    return;
}