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