我的问题是如何在不使用std :: stack库的情况下实现Stack :: top()函数?换句话说,我如何编写自己的top()函数来返回堆栈的顶部元素而不为其后续堆栈弹出它?
感谢。
#include <iostream>
#include <stdexcept>
using namespace std;
class Stack
{
private:
int *p;
int top,length;
public:
Stack(int = 0);
~Stack();
void push(int);
int pop();
void display();
};
Stack::Stack(int size)
{
top=-1;
length=size;
while(length <= 0) //If the stack size is zero, allow user to mention it at runtime
{
cout<<"Stack of zero size"<<endl;
cout<<"Enter a size for stack : ";
cin >> length;
}
p=new int[length];
}
Stack::~Stack()
{
delete [] p;
}
void Stack::push(int elem)
{
if(top==(length-1)) //If the top reaches to the maximum stack size
{
throw overflow_error("Can't push onto a full stack");
}
else
{
top++;
p[top]=elem;
}
}
int Stack::pop()
{
if(top==-1)
{
throw underflow_error("Can't pop from an empty stack");
}
int ret=p[top];
top--;
length--;
return ret;
}
void Stack::display()
{
for(int i = 0; i <= top; i++)
cout<<p[i]<<" ";
cout<<endl;
}
int main()
{
int len;
cout<<"Enter a size for stack : ";
cin >> len;
Stack s1(len);
try{
s1.push(1);
s1.display();
s1.push(2);
s1.push(3);
s1.push(4);
s1.push(5);
s1.display();
s1.pop();
s1.display();
s1.pop();
s1.display();
s1.pop();
s1.display();
s1.pop();
s1.display();
s1.pop();
s1.display();
}
catch(overflow_error){
cerr<< "Illegal operation. Cannot push onto a full stack.";
return -1;
}
catch(underflow_error){
cerr<< "Illegal operation. Cannot pop from an empty stack.";
return -1;
}
}
答案 0 :(得分:2)
由于您已经存储了top
,因此您只需返回p[top]
即可。换句话说:top()
基本上与pop()
相同,它只是不会删除顶部元素。