Question

I’d like to make a function that receives a 2-dimensional array and returns one of its rows (‘which’) as a simple array. I wrote this:

int *row(int *array, int lines, int columns, int which)
{
    int result[columns];

    for (int i=0; i<columns; i++)
    {
        result[i] = *array[which][i];
    }
    return result;
}

However, in line 7 I got the following error: invalid types ‘int[int]’ for array subscript. Any idea how to do this properly? I also tried to handle the 2D-array as an array of arrays, but didn’t succeed. I’m novice, so please avoid too advanced concepts.

Thanks for the help!

UPDATE: thanks for the help! Now my code looks like:

int n;  //rows
int m;  //columns
int data[100][100];   
int array[100];

int *row(int *array, int rows, int columns, int which)
{
    int* result = new int[columns];
    for (int i=0; i<columns; i++)
    {
        result[i] = *array[which*columns+i];
    }
    return result;
    delete[] result;
}

int main()
{
    array=row(data, n, m, 0);
}

I still get an error in main: incompatible types in assignment of ‘int*’ to ‘int [100]’

What could be the problem now? I also don’t know where to use the delete[] function to free up the array.

Thank you very much for the help!

Answer 1

You can’t just do this:

int result[columns];

You need a dynamic allocation:

int* result = new int[columns];

---

Also, your use of array looks wrong. If array is going to be a single pointer, then you want:

result[i] = array[which*columns + i];