用数组实现栈结构

//用数组实现栈结构
#include<iostream>
#include<string>
using namespace std;

void push(int *stack, int num, int &index, int stack_len)
{
    if (index >=  stack_len - 1)
        cout << "the stack is enough, please pop the data!" << endl; 
    else
    {
        ++index;
        stack[index] = num;
    }
}

void pop(int *stack, int &index)
{
    if (index <  0)
        cout << "the stack is empty, please push the data!" << endl; 
    else
    {
        cout << endl << '\t' <<stack[index];
        --index;
    }
}

void peak(int *stack, int &index)
{
    if (index <  0)
        cout << "the stack is empty, please push the data!" << endl; 
    else
    {
        cout << endl << '\t' <<stack[index];
    }
}

void show(int *stack, int &index)
{
    if (index <  0)
        cout << "the stack is empty, please push the data!" << endl; 
    else
    {
        for (int i = index; i >= 0; i--)
        cout << endl << '\t' <<stack[i];
    }
}

int main()
{
    int stack_len, num;
    cout << "please input the length of the stack:" << '\t';
    cin >> stack_len;
    int *stack = new int [stack_len];
    int index = -1;
    string str;
    cout << endl << "input data. please select the method: push pop peak show exit: " << '\t';
    while(cin >> str)
    {
        cout << endl;
        if(str == "push")
        {
            cout << "please input the data: " << '\t';
            cin >> num;
            push(stack ,num , index, stack_len);
        }    
        else if(str == "pop")
            pop(stack, index);
        else if(str == "peak")
            peak(stack, index);
        else if(str == "show")
            show(stack, index);
        else if(str == "exit")
        {
            delete [] stack;
            return 0;
        }
        else
            cout << "try again" << endl;
        cout << endl << "input data. please select the method: push pop peak exit: " << '\t';
    }
    system("pause");
    return 0;
}