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#include <iostream>
using namespace std;
//double pass[3][3]={{1,2,3},{0,1,4}, {5,6,0}} ;// the matrix that is entered by user
float inverse(float A[][3])
{
//float A[][3];// the matrix that is entered by user
float B[3][3];//the transpose of a matrix A
float C[3][3];//the adjunct matrix of transpose of a matrix A not adjunct of A
float X[3][3];//the inverse
int i,j;
double x,n=0;//n is the determinant of A
//cout<<"========== Enter matrix A =============================================\n";
//for(i=0;i<3;i++)
//{ cout<<endl;
// for(j=0;j<3;j++)
// {
// cout<<" A["<<i<<"]["<<j<<"]= ";
// cin>>A[i][j];
// B[i][j]=0;
// C[i][j]=0;
// }
//}
for(i=0,j=0;j<3;j++)
{
if(j==2)
n+=A[i][j]*A[i+1][0]*A[i+2][1];
else if(j==1)
n+=A[i][j]*A[i+1][j+1]*A[i+2][0];
else
n+=A[i][j]*A[i+1][j+1]*A[i+2][j+2];
}
for(i=2,j=0;j<3;j++)
{
if(j==2)
n-=A[i][j]*A[i-1][0]*A[i-2][1];
else if(j==1)
n-=A[i][j]*A[i-1][j+1]*A[i-2][0];
else
n-=A[i][j]*A[i-1][j+1]*A[i-2][j+2];
}
// cout<<"\n========== The matrix A is ==========================================\n";
for(i=0;i<3;i++)
{
cout<<endl;
for(j=0;j<3;j++)
{
A[i][j]; // cout<<" A["<<i<<"]["<<j<<"]= "<<A[i][j];
}
}
cout<<endl<<endl;
//cout<<"=====================================================================\n"<<endl;
//cout<<"The determinant of matrix A is "<<n<<endl<<endl;
//cout<<"====================================================================="<<endl;
if(n!=0) x=1.0/n;
else
{
cout<<"Division by 0, not good!\n";
cout<<"=====================================================================\n"<<endl;
return 0;
}
//cout<<"\n========== The transpose of a matrix A ==============================\n";
for(i=0;i<3;i++)
{
//cout<<endl;
for(j=0;j<3;j++)
{
B[i][j]=A[j][i];
B[i][j];// cout<<" B["<<i<<"]["<<j<<"]= "<<B[i][j];
}
}
// cout<<endl<<endl;
C[0][0]=B[1][1]*B[2][2]-(B[2][1]*B[1][2]);
C[0][1]=(-1)*(B[1][0]*B[2][2]-(B[2][0]*B[1][2]));
C[0][2]=B[1][0]*B[2][1]-(B[2][0]*B[1][1]);
C[1][0]=(-1)*(B[0][1]*B[2][2]-B[2][1]*B[0][2]);
C[1][1]=B[0][0]*B[2][2]-B[2][0]*B[0][2];
C[1][2]=(-1)*(B[0][0]*B[2][1]-B[2][0]*B[0][1]);
C[2][0]=B[0][1]*B[1][2]-B[1][1]*B[0][2];
C[2][1]=(-1)*(B[0][0]*B[1][2]-B[1][0]*B[0][2]);
C[2][2]=B[0][0]*B[1][1]-B[1][0]*B[0][1];
//cout<<"\n========== The adjunct matrix of transpose of the matrix A ==========\n";
for(i=0;i<3;i++)
{
cout<<endl;
for(j=0;j<3;j++)
{
C[i][j];// cout<<" C["<<i<<"]["<<j<<"]= "<<C[i][j];
}
}
// cout<<endl<<endl;
for(i=0;i<3;i++)
{
for(j=0;j<3;j++)
{
X[i][j]=C[i][j]*x;
}
}
//cout<<"\n========== The inverse matrix of the matrix you entered!!! ==========\n";
for(i=0;i<3;i++)
{ //cout<<endl;
for(j=0;j<3;j++)
{
X[i][j];// cout<<" X["<<i<<"]["<<j<<"]= "<<X[i][j];
}
}
//cout<<endl<<endl;
return float X[3][3];
}
float main()
{
int i,j;
float pass[][3] = {{1,2,3},{0,1,4},{5,6,0}}; // the matrix that is entered by user
float * test;
test[][] = inverse(pass);
cout<<"\n========== The inverse matrix of the matrix you entered!!! ==========\n";
for(i=0;i<3;i++)
{
cout<<endl;
for(j=0;j<3;j++)
{
cout<<" test["<<i<<"]["<<j<<"]= "<<endl;
}
}
}
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