包含min函数的栈的c++实现

题目：

定义栈的数据结构，要求添加一个min函数，能够得到栈的最小元素。
要求函数min、push以及pop的时间复杂度都是O(1)。

C++实现：

输入格式是：

1 10

2

1 代表push，后面的数字是要push的内容，2代表pop

代码如下：

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

template <class T>
class MinStackElement
{
public:
    T data; // the data stored
    T min; // the minimum element under the current element
};

template <class T>
class MinStack
{
public:
    MinStack(int max_size);
    void push(T new_data);
    T pop();
    T minElement();

private:
    MinStackElement<T> *elements;
    int size;
    int top;
};

template <class T>
MinStack<T>::MinStack(int max_size)
{
    elements = new MinStackElement<T>[max_size];
    size = max_size;
    top = 0;
}

template <class T>
void MinStack<T>::push(T new_data)
{
    top ++;
    elements[top - 1].data = new_data;

    if(top == 1)
    {
        elements[top - 1].min = new_data;
    }
    else
    {
        if(new_data < elements[top - 2].min)
        {
            elements[top - 1].min = new_data;
        }
        else
        {
            elements[top - 1].min = elements[top - 2].min;
        }
    }
}

template <class T>
T MinStack<T>::pop()
{
    if(top == 0)
        return T();

    T value;
    
    value = elements[top - 1].data;
    top --;
    return value;
}

template <class T>
T MinStack<T>::minElement()
{
    return elements[top - 1].min;
}

int main() {
    ifstream fin ("minstack.in");
    ofstream fout ("minstack.out");
    int instruction, num;
    MinStack<int> min_stack(50);
    
    if(fin.good() == false)
    {
        fout << "file open failed" << endl;
        return 0;
    }
    
    while(true)
    {
        if(fin.eof())
            break;
        
        fin >> instruction;
            
        if(instruction == 1)
        {
            fin >> num;
            min_stack.push(num);
            fout << "push : " << num << ", the minimum element : " << min_stack.minElement() << endl;
        }
        else if(instruction == 2)
        {
            num = min_stack.pop();
            fout << "pop : " << num << ", the minimum element : " << min_stack.minElement() << endl;
        }
    }
}

样例输入：

1 10
1 4
1 11
1 5
1 8
1 90
2
2
1 6
1 2
1 30
2
2

样例输出：

push : 10, the minimum element : 10
push : 4, the minimum element : 4
push : 11, the minimum element : 4
push : 5, the minimum element : 4
push : 8, the minimum element : 4
push : 90, the minimum element : 4
pop : 90, the minimum element : 4
pop : 8, the minimum element : 4
push : 6, the minimum element : 4
push : 2, the minimum element : 2
push : 30, the minimum element : 2
pop : 30, the minimum element : 2
pop : 2, the minimum element : 4