代码

//ikj
#define idx(i, j) ((i) * n + (j))

void matrix_multiply(int n, const double *A, const double *B, double *C) {
	for (int i = 0; i < n; i++)
		for (int k = 0; k < n; k++)
			for (int j = 0; j < n; j++)
				C[idx(i, j)] += A[idx(i, k)] * B[idx(k, j)];
}

评测结果