#数据结构#什么是栈及栈的作用

定义：一种可以实现“先进后出”的数据存储结构

分类：静态栈：以数组为内核        动态栈：以链表为内核

算法：入栈（压栈）/出栈

应用：函数调用、中断、表达式求职、内存分配、缓冲处理、迷宫

【参考程序历程】

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

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

typedef struct Stack
{
    PNODE pTop;
    PNODE pBottom;
}STACK, * PSTACK;

void init(PSTACK);//初始化
void push(PSTACK, int);//压栈
void traverse(PSTACK);//遍历
bool pop(PSTACK, int *);//出栈
void clear(PSTACK pS);//清除


int main(void)
{
    STACK S;
    int val;

    init(&S);//创建一个空栈
    push(&S, 1);//压栈
    push(&S, 2);//
    push(&S, 3);
    push(&S, 4);
    push(&S, 5);
    push(&S, 6);

    traverse(&S);//遍历输出

    clear(&S);

    if( pop(&S, &val) )
    {
        printf("出栈成功，出栈元素为%d
", val);
    }
    else
    {
        printf("出栈失败！
");
    }
    traverse(&S);

    return 0;
}

void init(PSTACK pS)
{
    pS->pTop = (PNODE)malloc(sizeof(NODE));//动态分配一块内存(在堆中分配)，
    if(NULL == pS->pTop)
    {
        printf("动态内存分配失败!
");
        exit(-1);
    }
    else
    {
        pS->pBottom = pS->pTop;
        pS->pTop->pNext = NULL;
    }
}

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

    pNew->data = val;
    pNew->pNext = pS->pTop;

    pS->pTop = pNew;

    return;

}

void traverse(PSTACK pS)
{
    PNODE p = pS->pTop;
    while(p != pS->pBottom)
    {
        printf("%d
", p->data);
        p = p->pNext;
    }
    printf("
");
}

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

bool pop(PSTACK pS, int * pVal)
{
    if(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(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;
    }
}