2- 栈的功能实现

数据结构3

1、线性结构的两种常见应用之一 栈 (存储数据的结构)
定义

• 一种可以实现“先进后出” 的存储结构
• 栈类似于箱子

2、分类

• 静态栈 （类似于用数组实现）
• 动态栈 （类似于用链表实现）

3、算法（往里放，从里取）

• 出栈
• 压栈（参看Java中线程的例子，成产消费的例子

4、栈的示意图

2-1 程序实现静态栈功能

# include <stdio.h>
# include <malloc.h>
/*如静态变量p和m是在栈中分配，有操作系统自动分配和释放。
 而(int *)malloc(100);执行后，将在堆中分配一块100字节的内存，由程序员手动分配。*/
void f(int k)
{
	int m;

	double * q = (double *)malloc(200);
}

int main(void)
{
	int i = 10;
	int * p = (int *)malloc(100);

	return 0;
}

代码实现2

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

typedef struct Node
{
	int data; //数据域
	struct Node * pNext;  //指针域
}NODE, * PNODE;


//创建栈数据类型
typedef struct Stack
{
	PNODE pTop;   //指针顶部
	PNODE pBottom; //指针底部
}STACK, * PSTACK;  //PSTACK 等价于 struct STACK *

void init(PSTACK);  //初始化
void push(PSTACK, int ); //压栈
void traverse(PSTACK);   //遍历输出
bool pop(PSTACK, int *); //出栈
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, 2);
	push(&S, 3);
	push(&S, 4);
	push(&S, 5);
	push(&S, 6);
	traverse(&S); //遍历输出
	
	clear(&S);
	//traverse(&S); //遍历输出

	if ( pop(&S, &val) )
	{
		printf("出栈成功，出栈的元素是%d\n", val);
	}
	else
	{
		printf("出栈失败!\n");
	}

	traverse(&S); //遍历输出

	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!\n");
		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->Top不能改成pS->Bottom
	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，并把出栈的元素存入pVal形参所指向的变量中，如果出栈失败，返回false,否则返回true
bool pop(PSTACK pS, int * pVal)
{
	if ( empty(pS) ) //pS本身存放的就是S的地址
	{
		return false;
	}
	else
	{
		PNODE r = pS->pTop;
		*pVal = r->data;
		pS->pTop = r->pNext;
		free(r);
		r = NULL;

		return true;
	}
}

//clear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;
	}
}