matrix multiplied by a vector in C - c

Question

I have a matrix[2][3], a vector[3] and I am computing the result of this with the below code which works perfectly fine.
My approach: Initialize a product matrix of size [3][2] to zero, perform the computation as in the function matrix_x_vector and extract the last row to get the final output(vector).
What I expect: Instead of using a product matrix of size [3][2] and then extracting the vector from it, is there any direct way of multiplying a matrix by a vector and store it directly into a resultant vector.
#include <stdio.h>
int main()
{
// Define Variables
int n1 = 2, n2= 3;
int vector[3] = {2,1,2};
int matrix[2][3] = {
{1,-1,2},
{2,-3,1},
};
int Product_matrix[3][2] = {
{0},
{0},
{0}
};
// Define Functions
void matrix_x_vector(int n1,int n2, int vector[n2], int matrix[n1][n2], int Product[n1][n2]); // Performs the calculation
// Execute Functions
matrix_x_vector(n1, n2, vector, matrix, Product_matrix);
printf("\n");
return 0;
}
void matrix_x_vector(int n1,int n2, int vector[n2], int matrix[n1][n2], int Product[n1][n2])
{
int i, j; // i = row; j = column;
printf("\nProduct Matrix of [x]*[y]\n");
// Load up A[n][n]
for (i=0; i<n2; i++)
{
for (j=0; j<n1; j++)
{
Product[j][0] += matrix[j][i] * vector[i];
printf("%4i", Product[j][0]);
}
printf("\n");
}
printf("Vector: \n");
// Print Vector from Product[n][n]
for (i=0; i<n1; i++){
printf("%4i\n", Product[i][0]);
}
}
Product Matrix of [x]*[y]
2 4
1 1
5 3
Vector:
5
3

Answer 1

If I understood the question correctly, it is asked for a function which uses a vector instead of a matrix for the result type. This function can be formulated as follows.
void matrix_x_vector_new(int n1,
int n2,
int vector[3],
int matrix[2][3],
int result_vector[3])
{
int i, j; // i = row; j = column;
printf("\nProduct Matrix of [x]*[y]\n");
// Load up A[n][n]
for (i = 0; i<n2; i++)
{
for (j = 0; j<n1; j++)
{
result_vector[j] += matrix[j][i] * vector[i];
printf("%4i", result_vector[j]);
}
printf("\n");
}
printf("Vector: \n");
// Print Vector from Product[n][n]
for (i = 0; i<n1; i++)
{
printf("%4i\n", result_vector[i]);
}
}