matrix.cpp

/**

Compile with
    g++ matrix.cpp -o matrix

Run with
    ./matrix

*/

#include <vector>
#include <iostream>
#include <cmath>

#include <malloc.h>

using namespace std;
#define SIZE 3

double Determinant(double**,int);

int main() {
    double a[SIZE][SIZE] = { {1,1,3}, {3,2,3}, {3,3,2} };

    double** minerals = new double*[SIZE];
    for (int i=0; i<SIZE; i++) {
        minerals[i] = new double[SIZE];
        for (int j=0; j<SIZE; j++) {
            minerals[i][j] = a[i][j];
        }
    }

    // TODO your code
    double result = Determinant(minerals, SIZE);
    cout << result << endl; // result should be 7

    // remember to free your allocated memory
    for (int i=0; i<SIZE; i++) {
        delete [] minerals[i];
    }
    delete [] minerals;
}

/*
   Recursive definition of determinate using expansion by minors.
*/
double Determinant(double **a,int n)
{
   int i,j,j1,j2;
   double det = 0;
   double **m = NULL;

   if (n < 1) { /* Error */

   } else if (n == 1) { /* Shouldn't get used */
      det = a[0][0];
   } else if (n == 2) {
      det = a[0][0] * a[1][1] - a[1][0] * a[0][1];
   } else {
      det = 0;
      for (j1=0;j1<n;j1++) {
         m = (double**)malloc((n-1)*sizeof(double *));
         for (i=0;i<n-1;i++)
            m[i] = (double*)malloc((n-1)*sizeof(double));
         for (i=1;i<n;i++) {
            j2 = 0;
            for (j=0;j<n;j++) {
               if (j == j1)
                  continue;
               m[i-1][j2] = a[i][j];
               j2++;
            }
         }
         det += pow(-1.0,j1+2.0) * a[0][j1] * Determinant(m,n-1);
         for (i=0;i<n-1;i++)
            free(m[i]);
         free(m);
      }
   }
   return(det);
}