栈的基本操作--插入，取栈顶元素，删除栈顶，清空栈

试了机组数据都对了。我忘了一部分c语言容错的语句了，没办法写得尽如人意。

 

#include<iostream>

#include<stdlib.h>

using namespace std;

struct stack{

	int size;

	int *top,*base;

};

stack a;

const int stacksize=10;

int top()

{

	int e;

	if(a.top==a.base)

		return -1;

	e=*(a.top-1);

	return e;

}

void insert(int e)

{

	if(a.top-a.base>=a.size)

	{

		a.base=(int*)realloc(a.base,(a.size+stacksize)*sizeof(int));

		a.top=a.base+a.size;

		a.size=a.size+stacksize;

	}

	*a.top=e;

	a.top=a.top+1;

}

void pop()

{

	if(a.top==a.base)

	{

		cout<<"error"<<endl;

		return;

	}

	a.top-=1;

}

void clear()

{

	while(a.top>a.base)

	{

		pop();

	}

}

int main()

{

	int n,i,traget,ko;

	a.size=stacksize;

	a.base=(int*)malloc(a.size*sizeof(int));

	a.top=a.base;

	cin>>n;

	for(i=1;i<=n;i++)

	{

		if(a.top-a.base>=a.size)

		{

			a.base=(int*)realloc(a.base,(a.size+stacksize)*sizeof(int));

			if(!a.base)

				exit(OVERFLOW);

			a.top=a.base+a.size;

		    a.size=a.size+stacksize;

		}

		cin>>*a.top;

		a.top=a.top+1;

	}

	cout<<top()<<endl;

	cin>>ko;

	insert(ko);

	cout<<top()<<endl;

	pop();

	cout<<top()<<endl;

	system("pause");

	return 0;

}