Matrix

Basic operations on square matrices.

26 lines tested

Usage: Matrix<int, 3> A; A.d = 1,2,3, 4,5,6, 7,8,9; array<int, 3> vec = 1,2,3; vec = (A^N) * vec;

content/data-structures/Matrix.h — Ulf Lundstrom, source: My head

template<class T, int N> struct Matrix {
	typedef Matrix M;
	array<array<T, N>, N> d{};
	M operator*(const M& m) const {
		M a;
		rep(i,0,N) rep(j,0,N)
			rep(k,0,N) a.d[i][k] += d[i][j] * m.d[j][k];
		return a;
	}
	array<T, N> operator*(const array<T, N>& vec) const {
		array<T, N> ret{};
		rep(i,0,N) rep(j,0,N) ret[i] += d[i][j] * vec[j];
		return ret;
	}
	M operator^(ll p) const {
		assert(p >= 0);
		M a, b(*this);
		rep(i,0,N) a.d[i][i] = 1;
		while (p) {
			if (p&1) a = a*b;
			b = b*b;
			p >>= 1;
		}
		return a;
	}
};