数据结构入门-栈

定义：一种可以实现“先进后出”的存储结构

分类：

1. 静态栈
2. 动态栈

算法：

1. 出栈
2. 压栈

代码实现：

多敲，多敲，后期改进

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


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


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


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


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

    init(&S); // 目的是造出一个空栈

    push(&S , 1); // 压栈
    push(&S , 8);
    push(&S , 23);
    push(&S , 26);
    push(&S , 34);
    push(&S , 45);
    push(&S , 76);
    push(&S , 88);
    traverse(&S); // 遍历输出

    if(pop(&S , &val))
    {
        printf("你删除的是%d\n", val );
        traverse(&S);
        printf("清空数据\n");
        clear(&S);
        traverse(&S);
    }
    else
    {
        printf("删除失败\n");
    }
}




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


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

    pNew->data = val; 

    pNew->pNext = pS->pTop; // 这里需要注意
    pS->pTop = pNew;

    return;
}


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

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

    printf("\n");
    return;
}


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

}


// 把pS所指向的栈出栈一次，并把出栈元素存下
bool pop(PSTACK pS , int *val)
{

    if (empty(pS))
    {
        return false;
    }
    else
    {
        PNODE p = pS->pTop;
        *val = p->data;

        pS->pTop = p->pNext;
        free(p);
        p = NULL;
        return true;

    }
    
}


// 清空
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;
    }
}

应用：

1. 函数调用
2. 中断
3. 表达式求值
4. 内存分配
5. 缓冲处理
6. 迷宫