Use array instead of vector in Matrix (#280)

Author: lrvideckis

content/data-structures/Matrix.h

@@ -6,7 +6,7 @@
  * Description: Basic operations on square matrices.
  * Usage: Matrix<int, 3> A;
  *  A.d = {{{{1,2,3}}, {{4,5,6}}, {{7,8,9}}}};
- *  vector<int> vec = {1,2,3};
+ *  array<int, 3> vec = {1,2,3};
  *  vec = (A^N) * vec;
  * Status: tested
  */
@@ -21,8 +21,8 @@ template<class T, int N> struct Matrix {
 			rep(k,0,N) a.d[i][j] += d[i][k]*m.d[k][j];
 		return a;
 	}
-	vector<T> operator*(const vector<T>& vec) const {
-		vector<T> ret(N);
+	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;
 	}