allocating a multi-dimensional array VSC++

Question

I am working with a 2D array in a VS2010 console application. I am allocating the array as such:

Thing::Thing(int _n, bool _control){
    m = _n;
    control = _control;
    thisArray = new int*[m];
    for(int ii = 0; ii < m; ii++){
        thisArray[ii] = new int[m];
        for (int jj = 0; jj < m; jj++){
            thisArray[ii][jj] = 0;
        }
    }
    if (control == true){
        int num = 1;
        for (int jj = 0; jj < m; jj++){
            for ( int ii = 0; ii<m; ii++){
                if ((jj == (m-1)) && (ii == (m-1))){
                    std::cout << "inserting " << 0 <<
                        "at[" << ii << "][" << jj << "]" << std::endl;
                    thisArray[ii][jj] = 0;
                    std::cout << thisArray[ii][jj] << std::endl;
                } else{
                    std::cout << "inserting " << num <<
                        "at[" << ii << "][" << jj << "]" << std::endl;
                    thisArray[ii][jj] = num++;
                    std::cout << thisArray[ii][jj] << std::endl;
                }
            }
        }
        pi.x = m-1;
        pi.y = m-1;
    }
}

then I attempt to display it through

void Thing::display(){
    int x = 0;
    int y = 0;
    for( ; y < m; y++){
        for( x = 0; x < m; x++){
            if (Point(x, y) == pi){
                std::cout << "[  ]";
            }
            std::cout << "[" << thisArray[x][y] << "]";
            if ( x == m ){
                std::cout << std::endl;
            }
        }
    }
}

but it seems like it is only displaying the first dimension as output when I pass in 4, and true looks like this:

inserting 1 at[0][0]1
inserting 2 at[1][0]2
inserting 3 at[2][0]3
inserting 4 at[3][0]4
inserting 5 at[0][1]5
inserting 6 at[1][1]6
inserting 7 at[2][1]7
inserting 8 at[3][1]8
inserting 9 at[0][2]9
inserting 10 at[1][2]10
inserting 11 at[2][2]11
inserting 12 at[3][2]12
inserting 13 at[0][3]13
inserting 14 at[1][3]14
inserting 15 at[2][3]15
inserting 0 at[3][3] 0
[1][2][3][4]

, and when I add the array to my watch list the system shows the pointer to pointer to a single value, and then will only show me the first element, and not all of the elements.

it throws no run time access errors, or anything like that, but when I try to display the array it only does the first row. Note: I have been asked to use an actual 2D-array of ints, and am not allowed to use a pre-written library, or a single dimensional lie.

edit: added additional output info. edit2 (resolved): in display changed the second for loop to be

for (x = 0; x < m; x++)

when holding values external to a for loop insure that they are reset for circular iteration.

come to think of it. this might be a logic error in the display() method, but still don't know why it only shows the first element in watches. — gardian06, Mar 05 '12 at 00:43

score 2 · Accepted Answer · edited May 23 '17 at 12:12

2

In your display function, you have to reset x at each iteration of the outer y loop. It would even be clearer, if you did the initialization within the for statement:

for(int y = 0; ; y < m; y++){
    for(int x = 0; ; x < m; x++){

And to view a pointer as an array in Visual C++ debugger, you can look at that other question.

edited May 23 '17 at 12:12

Community

1
1

answered Mar 05 '12 at 00:46

alexisdm

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thank you I had those separate so that I could use a Point to control the position, and must have forgot to change the second for loop to be for(x = 0; x < m; x++) – gardian06 Mar 05 '12 at 00:52

allocating a multi-dimensional array VSC++

1 Answers1