Fibonacci Number (Matrix Algorithm)

Fibonacci

#include <iostream>
using std::cin;
using std::cout;


class Matrix22 {
public:
	int data[2][2];
	Matrix22(int a11, int a12, int a21, int a22);
	Matrix22(const Matrix22 &matrix);
	Matrix22 power(int n);
	Matrix22& operator*=(const Matrix22 &target_matrix);
};


Matrix22::Matrix22(int a11, int a12, int a21, int a22){
	data[0][0] = a11;
	data[0][1] = a12;
	data[1][0] = a21;
	data[1][1] = a22;
}


Matrix22::Matrix22(const Matrix22 &matrix){
	data[0][0] = matrix.data[0][0];
	data[0][1] = matrix.data[0][1];
	data[1][0] = matrix.data[1][0];
	data[1][1] = matrix.data[1][1];
}


Matrix22 Matrix22::power(int n){
	Matrix22 t(*this);
	Matrix22 r(1, 0, 0, 1);
	while(n > 0){
		if(n % 2 == 1)
			r *= t;
		n /= 2;
		t *= t;
	}
	return r;
}


Matrix22& Matrix22::operator*=(const Matrix22 &target){
	int r[2][2], i, j;
	for(i=0; i<2; i++)
		for(j=0; j<2; j++)
			r[i][j] = data[i][0] * target.data[0][j] + data[i][1] * target.data[1][j];
	for(i=0; i<2; i++)
		for(j=0; j<2; j++)
			this->data[i][j] = r[i][j];
	return *this;
}


int main(int argc, char *argv[]){
	int n;
	cin >> n;
	if(n < 2){
		if(n == 1)
			cout << "1\n";
		else if(n == 2)
			cout << "2\n";
		return 0;
	}
	Matrix22 matrix(1, 1, 1, 0);
	Matrix22 result = matrix.power(n-2);
	cout << result.data[0][0] + result.data[0][1] << '\n';
	return 0;
}

No Zuo No Die. Why u Try.
CLASS