Question

This is my Code

#ifndef INTLIST_H_INCLUDED
#define INTLIST_H_INCLUDED
#include <iostream>
using namespace std;

class intList
{
    int upper_bound;
    int arr[0];
    public:
        intList(){ arr[0] = 0; upper_bound = 0; }
        void append(int x);
        void sort();
        friend ostream & operator << (ostream &, intList&);
        inline int len(){ return upper_bound; }
        inline int &operator [](int x){ return arr[x]; }
    private:
        void increment(int *a, int &l);
        void swap(int &a, int &b);
};

void intList::swap(int &a, int &b)
{
    int temp = a;
    a = b;
    b = temp;
}

void intList::increment(int *a, int &b)
{
    b++;
    a[b] = 0;
}

void intList::append(int num)
{
    arr[upper_bound] = num;
    increment(arr, upper_bound);
}

void intList::sort()
{
    for(int i = 0; i < upper_bound; i++)
    {
        int minLoc = i;
        for(int j = i+1; j<upper_bound; j++)
        {
            if(arr[j] < arr[minLoc])
                minLoc = j;
        }
        if(minLoc != i)
            swap(arr[i], arr[minLoc]);
    }
}

ostream& operator << (ostream & dout, intList &a)
{
    dout << "[ ";
    for(int i = 0; i<a.upper_bound-1; i++)
        dout << a.arr[i] << ", ";
    dout << a.arr[a.upper_bound-1] << " ]";

    return dout;
}

#endif // INTLIST_H_INCLUDED

The Code does its work perfectly fine. But at the end the Program Crashes. Giving some error like
process returned -1073741819 (0xC0000005) execution time : some seconds.

Just didn’t get where am I going wrong.

Answer 1

Your code has several problems.

For example, you have a fixed array of 0 size. If you want a dynamically growable array, you can use std::vector: you can add new items at the end of the vector (dynamically resizing it) using push_back() method:

#include <vector>

// Start with an empty vector
std::vector<int> v;

// Add some items to it
v.push_back(10);
v.push_back(20);
....

Note also that in header files it’s not good to insert a using namespace std;. In this way you pollute the global namespace with STL classes, which is bad. Just use std:: prefix in header files.

Moreover, if you want to print the class content to an output stream, you may want to take the class as a const reference, since instances of the class are input parameters (you observe them and print their content to the stream):

std::ostream& operator<<(std::ostream& os, const IntList& a)
{
   ....
}