array multiplication in c code example

Example 1: how to do matrix multiplication in c

double[][] c = new double[N][N];
for (int i = 0; i < N; i++)
{
 for (int j = 0; j < N; j++)
 	{
 for (int k = 0; k < N; k++)
 		{
		 c[i][j] += a[i][k] * b[k][j];
 		}
 	}
}

Example 2: matrix multiplication in c

#include <stdio.h>

// function to get matrix elements entered by the user
void getMatrixElements(int matrix[][10], int row, int column) {

   printf("\nEnter elements: \n");

   for (int i = 0; i < row; ++i) {
      for (int j = 0; j < column; ++j) {
         printf("Enter a%d%d: ", i + 1, j + 1);
         scanf("%d", &matrix[i][j]);
      }
   }
}

// function to multiply two matrices
void multiplyMatrices(int first[][10],
                      int second[][10],
                      int result[][10],
                      int r1, int c1, int r2, int c2) {

   // Initializing elements of matrix mult to 0.
   for (int i = 0; i < r1; ++i) {
      for (int j = 0; j < c2; ++j) {
         result[i][j] = 0;
      }
   }

   // Multiplying first and second matrices and storing it in result
   for (int i = 0; i < r1; ++i) {
      for (int j = 0; j < c2; ++j) {
         for (int k = 0; k < c1; ++k) {
            result[i][j] += first[i][k] * second[k][j];
         }
      }
   }
}

// function to display the matrix
void display(int result[][10], int row, int column) {

   printf("\nOutput Matrix:\n");
   for (int i = 0; i < row; ++i) {
      for (int j = 0; j < column; ++j) {
         printf("%d  ", result[i][j]);
         if (j == column - 1)
            printf("\n");
      }
   }
}

int main() {
   int first[10][10], second[10][10], result[10][10], r1, c1, r2, c2;
   printf("Enter rows and column for the first matrix: ");
   scanf("%d %d", &r1, &c1);
   printf("Enter rows and column for the second matrix: ");
   scanf("%d %d", &r2, &c2);

   // Taking input until
   // 1st matrix columns is not equal to 2nd matrix row
   while (c1 != r2) {
      printf("Error! Enter rows and columns again.\n");
      printf("Enter rows and columns for the first matrix: ");
      scanf("%d%d", &r1, &c1);
      printf("Enter rows and columns for the second matrix: ");
      scanf("%d%d", &r2, &c2);
   }

   // get elements of the first matrix
   getMatrixElements(first, r1, c1);

   // get elements of the second matrix
   getMatrixElements(second, r2, c2);

   // multiply two matrices.
   multiplyMatrices(first, second, result, r1, c1, r2, c2);

   // display the result
   display(result, r1, c2);

   return 0;
}

Example 3: array addition and multiplication in c

//This program is for matrix addition by programiz.com
#include <stdio.h>
int main() {
    int r, c, a[100][100], b[100][100], sum[100][100], i, j;
    printf("Enter the number of rows (between 1 and 100): ");
    scanf("%d", &r);
    printf("Enter the number of columns (between 1 and 100): ");
    scanf("%d", &c);

    printf("\nEnter elements of 1st matrix:\n");
    for (i = 0; i < r; ++i)
        for (j = 0; j < c; ++j) {
            printf("Enter element a%d%d: ", i + 1, j + 1);
            scanf("%d", &a[i][j]);
        }

    printf("Enter elements of 2nd matrix:\n");
    for (i = 0; i < r; ++i)
        for (j = 0; j < c; ++j) {
            printf("Enter element a%d%d: ", i + 1, j + 1);
            scanf("%d", &b[i][j]);
        }

    // adding two matrices
    for (i = 0; i < r; ++i)
        for (j = 0; j < c; ++j) {
            sum[i][j] = a[i][j] + b[i][j];
        }

    // printing the result
    printf("\nSum of two matrices: \n");
    for (i = 0; i < r; ++i)
        for (j = 0; j < c; ++j) {
            printf("%d   ", sum[i][j]);
            if (j == c - 1) {
                printf("\n\n");
            }
        }

    return 0;
}

Example 4: matrix multiplication in c

#include <stdio.h>
void enterData(int first[][10], int second[][10], int r1, int c1, int r2, int c2);
void multiplyMatrices(int first[][10], int second[][10], int multResult[][10], int r1, int c1, int r2, int c2);
void display(int mult[][10], int r1, int c2);

int main() {
    int first[10][10], second[10][10], mult[10][10], r1, c1, r2, c2;
    printf("Enter rows and column for the first matrix: ");
    scanf("%d %d", &r1, &c1);
    printf("Enter rows and column for the second matrix: ");
    scanf("%d %d", &r2, &c2);

    // Taking input until columns of the first matrix is equal to the rows of the second matrix
    while (c1 != r2) {
        printf("Error! Enter rows and columns again.\n");
        printf("Enter rows and columns for the first matrix: ");
        scanf("%d%d", &r1, &c1);
        printf("Enter rows and columns for the second matrix: ");
        scanf("%d%d", &r2, &c2);
    }

    // Function to take matrices data
    enterData(first, second, r1, c1, r2, c2);

    // Function to multiply two matrices.
    multiplyMatrices(first, second, mult, r1, c1, r2, c2);

    // Function to display resultant matrix after multiplication.
    display(mult, r1, c2);

    return 0;
}

void enterData(int first[][10], int second[][10], int r1, int c1, int r2, int c2) {
    printf("\nEnter elements of matrix 1:\n");

    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c1; ++j) {
            printf("Enter a%d%d: ", i + 1, j + 1);
            scanf("%d", &first[i][j]);
        }
    }
    printf("\nEnter elements of matrix 2:\n");

    for (int i = 0; i < r2; ++i) {
        for (int j = 0; j < c2; ++j) {
            printf("Enter b%d%d: ", i + 1, j + 1);
            scanf("%d", &second[i][j]);
        }
    }
}

void multiplyMatrices(int first[][10], int second[][10], int mult[][10], int r1, int c1, int r2, int c2) {

    // Initializing elements of matrix mult to 0.
    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c2; ++j) {
            mult[i][j] = 0;
        }
    }

    // Multiplying first and second matrices and storing in mult.
    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c2; ++j) {
            for (int k = 0; k < c1; ++k) {
                mult[i][j] += first[i][k] * second[k][j];
            }
        }
    }
}

void display(int mult[][10], int r1, int c2) {

    printf("\nOutput Matrix:\n");
    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c2; ++j) {
            printf("%d  ", mult[i][j]);
            if (j == c2 - 1)
                printf("\n");
        }
    }
}