// ma tran

#include<iostream.h>

#include<iomanip.h>

#include<conio.h>

class MT

{ int n,m;

float a[20][20];

public:

friend istream& operator>>(istream& is,MT &b);

friend ostream& operator<<(ostream& os,MT b);

friend int ktra(MT); // co the dung ham ban o ham nay

};

istream& operator>>(istream& is,MT &b)

{

cout<<"nhap so dong: ";is>>b.m;

cout<<"nhap so cot: ";is>>b.n;

for(int i=1;i<=b.m;i++)

for(int j=1;j<=b.n;j++)

{ cout<<"nhap a["<<i<<"]["<<j<<"]= ";

is>>b.a[i][j]; }

return(is);

}

ostream& operator<<(ostream& os,MT b)

{ cout<<setiosflags(ios::showpoint)<<setprecision(2); /*(2) la sau dau cham co 2-1=1 so sau dau cham */

for(int i=1;i<=b.m;i++)

for(int j=1;j<=b.n;j++)

{if(j==1) os<<"

";

os<<setw(5)<<b.a[i][j]; }

return(os);

}

int ktra(MT b)

{ int kq; float x[20][20];

if(b.n!=b.m) kq=0;

else

{

for(int i=1;i<=b.n;i++) // thanh lap 1 ma tran don vi de so sanh

for(int j=1;j<=b.n;j++)

{ x[i][j]=0;

x[i][i]=1; }

int dem=0;

for(i=1;i<=b.n;i++)

for(int k=1;k<=b.n;k++) /* chu y bien int k,ko dc viet bien j thay cho k*/

{

if((b.a[i][k]==x[i][k]))

dem=dem+1;

}

if(dem==b.n*b.n) kq=1;

else kq=0;

}

return(kq);

}

main()

{ MT b;

cout<<"

nhap ma tran can xet

";cin>>b;cout<<b; //ko dc viet ktra(b)

if(ktra(b)) cout<<"

ma tran vua nhap <la> ma tran don vi";

else cout<<"

ma tran vua nhap <khong> la ma tran don vi";

getch();

}