#include <stdio.h>
typedef struct {
  double data[1024]; // One-dimensional array stores data row-by-row
  int nrows;            // Number of rows
  int ncols;            // Number of columns
} Matrix;
void printMatrix(Matrix M);
Matrix matrixMult(Matrix A, Matrix B);
int main(void)
{
  Matrix A = { {1.2, 2.3,
                3.4, 4.5,
                5.6, 6.7},
               3,
               2};
  Matrix B = { {5.5, 6.6, 7.7,
                1.2, 2.1, 3.3},
               2,
               3}; 
  printMatrix(A);
  printMatrix(B);
  Matrix C = matrixMult(A, B);
  printMatrix(C);
  return 0;
}
void printMatrix(Matrix M){
  int i, j;
  printf("[\n");
  for (i = 0; i < M.nrows; i++) {
    for (j = 0; j < M.ncols; j++) {
      printf("%6.3f ", M.data[i * M.ncols + j]);
    }
    printf("\n");
  }
  printf("]\n\n");
}
Matrix matrixMult(Matrix A, Matrix B)
{
  Matrix C;
  if (A.ncols != B.nrows) {
    printf("Error: ncols of A does not equal nrows of B\n");
  }
  else {
    int i, j, k;
    double value;
    for (i = 0; i < A.nrows; i++) {
      for (j = 0; j < B.ncols; j++) {
	      value = 0.0;
	      for (k = 0; k < A.ncols; k++) {
	        value += A.data[i * A.ncols + k] * B.data[k * B.ncols + j];
	      }
	      C.data[i * A.nrows + j] = value;
      }
    }
    C.nrows = A.nrows;
    C.ncols = B.ncols;
  }
  return C;
}