[Why does the result for determinant is always 0?]

[heyitsme1998]

Is there anyone know why is the result of determinant is always 0? Thank you, Good people :)

  #include<iostream>
 
using namespace std;
 
int cofactor(int data[3][3],int x,int y)
{
    float cofactor_v;

    cofactor_v = data[(x + 1) % 3][(y + 1) % 3]
        * data[(x + 2) % 3][(y + 2) % 3]
        - data[(x + 1) % 3][(y + 2) % 3]
        * data[(x + 2) % 3][(y + 1) % 3];
        return cofactor_v;
}

int main(){
    int mat[3][3], i, j;
    float determinant = 0, cofactor_v;
    
    cout<<"Enter elements of matrix row wise:\n";
    for(i = 0; i < 3; i++)
        for(j = 0; j < 3; j++)
           cin>>mat[i][j];
    
    printf("\nGiven matrix is:");
    for(i = 0; i < 3; i++){
        cout<<"\n";
        for(j = 0; j < 3; j++)
            {
			cout<<mat[i][j];
			}
			}
			for(i = 0; i < 1; i++){
        	cout<<"\n";
        	for(j = 0; j < 1; j++)
            {
    		cout<<"\Nilai kofaktor matriks adalah="<<cofactor(mat,0,0)<<cofactor(mat,1,1)<<cofactor(mat,0,2);
			
			}
		}
		//finding determinant
    	for (i = 0; i < 3; i++)
{
	for (j = 0; j < 3; j++)
	{
		if (i == 0)
			determinant += mat[0][j] * cofactor_v;
	}
}
cout<<"Determinan matriks adalah="<<determinant;

}

[lastchance]

Try

                //finding determinant
        for (j = 0; j < 3; j++)
        {
                        determinant += mat[0][j] * cofactor(mat,0,j);
        }
cout<<"Determinan matriks adalah="<<determinant;

If you are expanding using the first row then you probably want to change the middle cofactor that you are printing out on line 37 as well (and put some spaces in your output).

[Peter87]

cofactor_v is never initialized. The compiler should be able to warn you about simple problems like this. If you're using GCC, MinGW or Clang you should at least use the -Wall compiler flag.

https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wall