Problem with program output

Question

Below is my program and im having a problem with the determinant function.

File input is:

2
1 0
0 1
3
8 9 1
3 5 2
-2 3 -1
0

and for the second matrix it is reading nan for the result of the determinant function for matrix two in the input file, any ideas for what could be going wrong with my code?

#include <iostream>
#include <fstream>
#include <cmath>

using namespace std;

const int maxsize = 10;

ifstream fin;
ofstream fout;

void transpose (double omatrix[][maxsize],double tmatrix [][maxsize], int array_size)
{
    for(int i = 0; i < array_size; i++)
    {
        for(int j = 0; j < array_size; j++)
        {
            tmatrix[j][i] = omatrix[i][j];
        }


    }
}

void sub (double omatrix[][maxsize], double smatrix[][maxsize], int array_size, int i, int j)
{
    int counter1 = 0, counter2 = 0;

    for (int a = 0; a < array_size; a++)
    {
        if (a != i)
        {
            for (int b = 0; b < array_size; b++)
            {
                if (b != j)
                {
                    smatrix[counter1][counter2] = omatrix[a][b];
                    counter2++;
                }
            }
            counter1++;
        }
    }
}

double determininant(double original_matrix[][maxsize], int array_size)
{
    double D = 0.0, temp[maxsize][maxsize];

    if(array_size == 1)
    {
        return original_matrix[0][0];
    }

    else if(array_size == 2)
    {
        return (original_matrix[0][0] * original_matrix[1][1]) - (original_matrix[0][1] * original_matrix[1][0]);
    }
    for(int i = 0; i < array_size; i++)
    {
        sub (original_matrix,temp,array_size, 0, i);
        D += pow(-1.0,i) * original_matrix[0][i] * determininant(temp, array_size - 1);
    }
    return D;
}

void inverse(double omatrix[][maxsize], int array_size, double imatrix[][maxsize])
{
    double D = determininant(omatrix, array_size);
    double c[maxsize][maxsize];

    if (D != 0)
    {
        for(int i = 0; i < array_size; i++)
            {
                for(int j = 0; j < array_size; j++)
                {
                    sub (omatrix, c, array_size, i, j);
                    imatrix[j][i] = pow(-1.0, i+j) * determininant( c, array_size - 1) / D;
                }
            }
    }
}

void mult(double omatrix[][maxsize], double imatrix[][maxsize], double pmatrix[][maxsize], int array_size)
{
    for(int i = 0; i < array_size; i++)
            {
                for(int j = 0; j < array_size; j++)
                {
                    pmatrix[i][j] = 0;

                    for(int k = 0; k < array_size; k++)
                    {
                        pmatrix[i][j] += omatrix[i][k] *imatrix[k][j];
                    }
                }
            }
}

void print (const double m[][maxsize], int array_size)
{
    for(int i = 0; i < array_size; i++)
            {
                for(int j = 0; j < array_size; j++)
                {
                    fout << m[i][j] << "  ";
                }
                fout << "\n";
            }
            fout << "\n";
}


int main()
{
    double original_matrix[maxsize][maxsize],
           inverse_matrix [maxsize][maxsize],
           transposed_matrix[maxsize][maxsize],
           product_matrix [maxsize][maxsize],
           D;


    int array_size;

    fout.setf(ios::fixed);
    fout.precision(2);

    char File_Name[10];
    cout << "Please enter a name for the output file";
    cin >> File_Name;

    fin.open ("input.txt");
    fout.open (File_Name);

    if (fin.fail())
    {
        cout << "Input file opening failed. \n";
        return 0;
    }

    while(fin >> array_size)
    {
        if(array_size != 0)
        {
            for(int i = 0; i < array_size; i++)
            {
                for(int j = 0; j < array_size; j++)
                {
                    fin >> original_matrix[i][j];
                }
            }

            fout << "THE ORIGIONAL ARRAY! \n";
            print (original_matrix, array_size);
            transpose (original_matrix, transposed_matrix, array_size);
            fout << "THE TRANSPOSED VIRSION! \n";
            print (transposed_matrix, array_size);
            fout << determininant(original_matrix, array_size) << "\n\n";
            inverse(original_matrix, array_size, inverse_matrix);
            print (inverse_matrix, array_size);
            mult(original_matrix, inverse_matrix, product_matrix, array_size);
            print (product_matrix, array_size);


        }
    }

    fin.close();
    fout.close();

    return 0;
}

The output is:

THE ORIGIONAL ARRAY! 
1.00  0.00  
0.00  1.00  

THE TRANSPOSED VIRSION! 
1.00  0.00  
0.00  1.00  

1.00

1.00  -0.00  
-0.00  1.00  

1.00  0.00  
0.00  1.00  

THE ORIGIONAL ARRAY! 
8.00  9.00  1.00  
3.00  5.00  2.00  
-2.00  3.00  -1.00  

THE TRANSPOSED VIRSION! 
8.00  3.00  -2.00  
9.00  5.00  3.00  
1.00  2.00  -1.00  

nan                              <--------------------- is wrong should be -78.00
                                                        which makes the next 2 mess up.
0.00  -0.00  0.00  
-0.00  0.00  -0.00  
0.00  -0.00  0.00  

0.00  0.00  0.00  
0.00  0.00  0.00  
0.00  0.00  0.00  

Answer 1

You are forgetting to reset counter2 in sub(...). So you are copying into the wrong place in the result matrix, and using uninitialized memory in your calculations.

(The moral of the story is to declare variables in the smallest possible scope where you actually need them.)