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//Title of this code
//clang 3.5.0

#include <iostream>

#include<iostream>
#include<fstream>
using namespace std;
template <class T>
class Matrix{
public:
    Matrix();
    Matrix(T diagonal);

template <class H>
    friend ostream& operator <<(ostream& outs, const Matrix<H> &obj);
    template <class H>
    friend istream& operator >>(istream& in, Matrix<H> &obj);
    template <class H>
    friend Matrix<H> operator *(const Matrix<H>& A, const Matrix<H>& B);

private:
    const static int n=3;
    T a[n][n];

};//class declaration

template <class T>
Matrix<T>::Matrix(){
    for (int i=0;i<n;i++)
        for (int j=0;j<n;j++)
            a[i][j]=0;
}
template <class T>
Matrix<T>::Matrix(T diagonal){
    for (int i=0;i<n;i++)
        for (int j=0;j<n;j++)
            if (i==j)
                a[i][j]=diagonal;
            else
                a[i][j]=0;
}
template <class T>
ostream& operator <<(ostream& outs, const Matrix<T> & obj)
{
    for (int i = 0; i < obj.n; i++){
        for (int j = 0; j < obj.n; j++)
            outs << " "<< obj.a[i][j];
        outs<<endl;
    }
    outs<<endl;
    return outs;
}
template <class T>
istream& operator >>(istream& in, Matrix<T> & obj)
{
    for (int i = 0; i < obj.n; i++){
        for (int j = 0; j < obj.n; j++){

in >> obj.a[i][j];
        }
    }
    return in;
}
template<class T>
Matrix<T> operator *(const Matrix<T>& A, const Matrix<T>& B){
    Matrix<T> product;
    for (int i=0;i<A.n; i++)
        for (int j=0;j<A.n; j++) {
            T sum=0;
            for (int k=0; k<A.n; k++)
                sum = sum+A.a[i][k]*B.a[k][j];
            product.a[i][j]=sum;
        }
    return product;
}

int main(){
    Matrix<int>  A;
    Matrix<int>  B(2);
    cout << A;
    cout <<B;

cout <<"stop here";

ifstream fin;
    ofstream fout;
    fout.open("output.txt");
    if (fout.fail()){
        cout <<"error openning output file";
        exit(1);
    }

fin.open("input.txt");
    if (fin.fail()){
        cout <<"error openning input file";
        exit(1);
    }

//input matrix C
    Matrix<int> C;
    cin >>C;
    //fin >>C;
    cout <<"C = "<<endl<<C<<endl;
    cout <<"B = "<<endl<<B<<endl;
    cout <<"C*B = "<<endl<<C*B<<endl;
    //fout <<C;
    //cout <<C.det();

return 0;

}

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Compilation time: 0.93 sec, absolute running time: 0.15 sec, cpu time: 0 sec, memory peak: 3 Mb, absolute service time: 1.11 sec