Question

I am making a c++ program which should read in from standard input an integer N. It should then read from a file “data.txt” values into an array of size N. then it should pass it to a function which reverses the array and returns a pointer to the new array. Then it should print the contents of the returned pointer’s array. But everytime I run the program it crashes. Any ideas?

#include <iostream>
#include <fstream>

using namespace std;

int * reverseArray(int * arr, const int size)
{
//int arr1[size];
int *arr2 = new int[size];
for(int iii = 0; iii < size; iii++)
{
    (*(arr2+iii)) = (*(arr + size - 1 - iii));
}

return arr2;
}

int main()
{
int N;
cin >> N;
if(N >= 0 && N <= 50)
{
    ifstream inputFile;
    inputFile.open("data.txt");
    int *arr = new int[N];
    int iii = 0;
    while(inputFile >> (*(arr+iii)) && iii < N)
    {    iii++;}

    arr = reverseArray(arr, N);

    for(int jjj = 0; jjj < N; jjj++)
    {
        cout << (*(arr+jjj)) << endl;
    }

    delete [] arr;
    inputFile.close();
}

return 0;
}

Answer 1

I think the problem is here:

while(inputFile >> (*(arr+iii)) && iii < N)

The check to ensure iii is less than N occurs after the access. Reorder the conditions:

while(iii < N && inputFile >> (*(arr+iii)) )

Note this line introduces a memory leak:

arr = reverseArray(arr, N);

As this is C++ consider using std::vector<int> instead.