链栈初始化、进栈、出栈、判空、遍历、求长、求顶、清栈、毁栈

    栈是限定仅在表尾进行插入或者删除的操作受限的线性表;表头端称为栈底，表尾端称为栈顶。

    链栈判空：S->next=NULL;

    链栈判不存在：S=NULL；

#include "stdafx.h"
#include "iostream"
using namespace std;
typedef int ElemType;
typedef int Status;
typedef struct SNode {
	ElemType data;
	struct SNode *next;
}SNode, *LinkedStack;
//初始化栈
Status initLinkedStack(LinkedStack &S) {  //链式栈结构无头节点
	S = new SNode;
	if (!S)
	{
		cout << "内存分配失败！" << endl;
		return false;
	}
	S->next = NULL;
	return true;
}
//向栈中插入元素
Status push(LinkedStack &S, int e) {
	LinkedStack p;
	p = new SNode;   //新建节点
	if (!p)
	{
		cout << "内存分配失败！" << endl;
		return false;
	}
	p->data = e;
	p->next = S->next;    //将元素插入栈顶
	S->next = p;
	return true;
}

//判断某个节点是否为空
Status isEmpty(LinkedStack &S) {
	if (S == NULL)
	{
		cout << "栈不存在！" << endl;
		exit(0);
	}
	if (S->next == NULL)
		return true;
	else
		return false;
}
//输出函数
Status visit(ElemType e) {
	cout << e << "   ";
	return true;
}
//遍历链式栈
Status stackTraverse(LinkedStack &S) {
	if (isEmpty(S))
	{
		cout << "链表为空！" << endl;
		exit(0);
	}
	LinkedStack p;
	p = S->next;
	while (p)
	{
		visit(p->data);
		p = p->next;
	}
	cout << endl;
	return true;
}
//求长
Status getLength(LinkedStack &S) {
	ElemType length = 0;
	LinkedStack p;
	p = S->next;
	while (p)
	{
		++length;
		p = p->next;
	}
	return length;
}
//获取栈顶元素
Status getTop(LinkedStack &S) {
	return S->next->data;
}
//出栈，并返回出栈元素的值
Status pop(LinkedStack &S) {
	int e;
	if (isEmpty(S))
	{
		cout << "链栈为空！" << endl;
		exit(0);
	}
	LinkedStack p;
	p = S->next;
	e = p->data;
	S->next = p->next;
	delete p;
	return e;
}
//清空链栈
Status clearStack(LinkedStack &S) {
	while (!isEmpty(S)) {
		pop(S);
	}
	return true;
}
//销毁栈
Status destroyStack(LinkedStack &S) {
	while (!isEmpty(S))
	{
		pop(S);
	}
	delete S;
	S = NULL;
	return true;
}
int main()
{
	ElemType e;
	LinkedStack stack;
	cout << "初始化链栈" << endl;
	initLinkedStack(stack);
	cout << "请输入第一个元素：";
	cin >> e;
	push(stack, e);
	cout << "请输入第二个元素：";
	cin >> e;
	push(stack, e);
	cout << "请输入第三个元素：";
	cin >> e;
	push(stack, e);
	cout << "该链栈为：";
	stackTraverse(stack);
	cout << "链表长度为：";
	cout << getLength(stack) << endl;
	cout << "栈顶元素为：" << getTop(stack) << endl;
	cout << "执行一次出栈操作，出栈元素为：" << pop(stack) << endl;
	cout << "执行清栈操作" << endl;
	clearStack(stack);
	stackTraverse(stack);
	cout << "执行毁栈操作" << endl;
	destroyStack(stack);
	isEmpty(stack);
	return 0;
}