代码

#define idx(i, j) ((i) * n + (j))
double H[1<<20];
void matrix_multiply(int n, const double *A, const double *B, double *C) {
	for (int i = 0; i < n; i++) 
		for (int j = 0; j < n; j++) H[idx(i, j)]=B[idx(j, i)];
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			double t = 0;
			for (int k = 0; k < n; k++) {
				t += A[idx(i, k)] * H[idx(j, k)];
			}C[idx(i, j)]=t;
		}
	}
}

评测结果