multidimensional array function outputting garbage?

Question

I have this function meant to initialize a multidimensional 2d (6x6) array to zero. I call the function in main using cout to test it and it outputs garbage. Please help. Thanks!

int** initializeArray(void)
{
    typedef int* rollArray;     //this line is actually outside of the function in my
                                //program
int i, j;
rollArray *m = new rollArray[6];

for (i = 0; i < 6; i++)
    m[i] = new int[6];

for (i = 0; i < 6; i++)
    for (j = 0; j < 6; j++)
        m[i][j] = 0;

return m;
}

Fix your code indentation please

Borgleader
– Borgleader

2013-07-18 23:19:32 +00:00
Commented Jul 18, 2013 at 23:19 — Borgleader
– Borgleader, Commented Jul 18, 2013 at 23:19
You are initializing a one dimensional array...

Dummy Code
– Dummy Code

2013-07-18 23:20:47 +00:00
Commented Jul 18, 2013 at 23:20 — Dummy Code
– Dummy Code, Commented Jul 18, 2013 at 23:20
Include your test code that outputs garbage.

Yakk - Adam Nevraumont
– Yakk - Adam Nevraumont

2013-07-18 23:20:50 +00:00
Commented Jul 18, 2013 at 23:20 — Yakk - Adam Nevraumont
– Yakk - Adam Nevraumont, Commented Jul 18, 2013 at 23:20

user2530166 · Accepted Answer · 2013-07-18 23:25:01Z

1

If the value 6 is known at compile-time, I would suggest using std::array in a nested fashion. For example:

#include <array>
#include <iostream>

int main()
{
    std::array<std::array<int,6>,6> a = {0};

    for (int i = 0; i < 6; ++i)
    {
        for (int j = 0; j < 6; ++j)
        {
            std::cout << a[i][j] << std::endl; // Prints 0.
        }
    }

    return 0;
}

In fact, you won't even need to create a function to initialize your array. Declare your nested array and you are good to go. (If you don't know the dimension at compile-time, you could use std::vector in a similar fashion.)

answered Jul 18, 2013 at 23:25

user2530166

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3 Comments

Qaz Over a year ago

Even better, you can use ranged-for loops to print it.

user2530166 Over a year ago

True...how much C++11 should we introduce at once? :)

Qaz Over a year ago

As much as is needed to write safer or more readable code imo.

Ran Eldan · Accepted Answer · 2013-07-18 23:30:17Z

0

The problem is with your test.
How can you mess up such a simple test? Just use:

int ** a = initializeArray();
int i,j;
for (i = 0; i < 6; i++) {
    for (j = 0; j < 6; j++) {
        cout << a[i][j] << " "; 
    }
    cout << endl;
}

edited Jul 18, 2013 at 23:30

answered Jul 18, 2013 at 23:24

Ran Eldan

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