DS: 2 stacks using 1 array

/*
*   masfiq
*   17 march, 2017
*
*/
#include<iostream>
#include<cstdlib>
using namespace std;

class twoStacks
{
private:
    int *arr;
    int size;
    int top1;
    int top2;
public:
    twoStacks(int size)  //Constructor
    {
        this->size = size;
        this->arr = new int[size];
        top1 = -1;
        top2 = size;
    }
    void push1(int x)
    {
        if(top2 == top1+1)
        {
            cout<<"stack overflowed."<<endl;
            exit(1);
        }
        else
        {
            top1++;
            arr[top1] = x;
        }
    }
    void push2(int x)
    {
        if(top2 == top1+1)
        {
            cout<<"stack overflowed."<<endl;
            exit(1);
        }
        else
        {
            top2--;
            arr[top2] = x;
        }
    }
    int pop1()
    {
        if(top1 == -1)
        {
            cout<<"stack underflowed."<<endl;
            exit(1);
        }
        else
        {
            int x = arr[top1];
            top1--;
            return x;
        }
    }
    int pop2()
    {
        if(top2 == size)
        {
            cout<<"stack underflowed"<<endl;
            exit(1);
        }
        else
        {
            int x = arr[top2];
            top2++;
            return x;
        }
    }
void print_stack1(){
    for(int i=0; i<= top1; i++){
        cout<<arr[i]<<"->";
    }
    cout<<endl;
}
void print_stack2(){
    for(int i=size-1; i >= top2; i--){
        cout<<arr[i]<<"->";
    }
    cout<<endl;
}
};

int main()
{
    twoStacks ts(5);
    ts.push1(5);
    ts.push2(10);
    ts.push2(15);
    ts.push1(11);
    ts.push2(7);
    ts.print_stack1();
    ts.print_stack2();
//    cout << "Popped element from stack1 is " << ts.pop1();
//    ts.push2(40);
//    cout << "\nPopped element from stack2 is " << ts.pop2();

    return 0;
}
/*
    Output:
    5->11->
    10->15->7->
*/