rendered paste body public static Fraction det( Fraction m[][] ) { int countSwap = 0; for( int i = 0; i < m.length; i++ ) { if( m[i][i].equals( 0 ) ) for( int j = i + 1; j < m[i].length; j++ ) if( !m[j][i].equals( 0 ) ) { m = swapLine( j, i, m ); countSwap++; break; } for( int j = i; j < m.length; j++ ) { if( i != j ) { Fraction addFra = m[i][i].inv( ).mult( new Fraction( -1 ) ).mult( m[j][i] ); if( addFra.getDenominator( ) == 0 ) return null; m = addLine( i, j, addFra, m ); } } } Fraction ret = new Fraction( 1 ); for( int k = 0; k < m.length; k++ ) ret = ret.mult( m[k][k] ); if( countSwap % 2 != 0 ) ret = ret.mult( new Fraction( -1 ) ); return ret; }