How do you write a functions using pointers to multiply two matrices and return it to the calling function?

Answer 1

void main()

{

int a[10][10],b[10][10],c[10][10],i,j,k,m,n,p,q;

printf("Enter The Rows And Cloumns And Of The First Matrix:");

scanf("%d %d",&m,&n);

printf("\nEnter The Rows And Cloumns And Of The Second Matrix:");

scanf("%d %d",&p,&q);

printf("\nEnter Elements Of The First Matrix:\n");

for(i=0;i< m;i++)

{

for(j=0;j< n;j++)

{

scanf("%d",&a[i][j]);

}

}

printf("\nEnter Elements Of The Second Matrix:\n");

for(i=0;i< p;i++) {

for(j=0;j< q;j++)

scanf("%d",&b[i][j]);

}

printf("The First Matrix Is:\n"); /* Print the first matrix */

for(i=0;i< m;i++) {

for(j=0;j< n;j++)

printf(" %d ",a[i][j]);

printf("\n");

}

printf("The Second Matrix Is:\n"); /* Print the second matrix */

for(i=0;i< p;i++) {

for(j=0;j< q;j++)

printf(" %d ",b[i][j]);

printf("\n");

}

if(n!=p) {

printf("Aborting./nMultiplication Of The Above Matrices Not Possible.");

exit(0);

}

else {

for(i=0;i< m;i++) {

for(j=0;j< q;j++) {

c[i][j] = 0;

for(k=0;k< n;k++) {

c[i][j] = c[i][j] + a[i][k] * b[k][j];

}

}

}

printf("\nThe Product Of The Two Matrices Is:\n\n");

for(i=0;i< m;i++) {

for(j=0;j< q;j++) {

printf(" %d ",c[i][j]);

}

printf("\n");

}

}

return 0;

}

-----------------------------------------------------">-----------------------------------------------------

The above code is not the solution of Matrix multiplication using pointers.

the following code is absolutely correct.

void main()

{int *a,*b,*c,row1,col1,row2,col2;

clrscr();

printf("enter rows of 1at matrix");

scanf("%d",&row1);

printf("enter columns of 1at matrix");

scanf("%d",&col1);

printf("enter rows of 2nd matrix");

scanf("%d",&row2);

printf("enter columns of 2nd matrix");

scanf("%d",&col2);

if(col1!=row2)

{

printf("\nsorry\n");

}

else

{

a = (int *) malloc(row1*col1 * 2);

b = (int *) malloc(row2*col2 * 2);

c = (int *) malloc(col1*row2 * 2);

clrscr();

printf("enter 1st matrix \n");

insert(a,row1,col1);

getch();

clrscr();

printf("enter 2st matrix \n");

insert(b,row2,col2);

getch();

clrscr();

printf("1st matrix is\n");

display(a,row1,col1);

printf("\n2nd matrix is\n");

display(b,row2,col2);

prod(a,b,c,row1,col2);

printf("\nafter multiplication \n\n\n");

display(c,row1,col2);

}

getch();

}

insert(int *q,int r,int c)

{int i,j;

for(i=0;i

{

for(j=0;j

{ printf("\nEnter [%d][%d] element-- ",i,j);

scanf("%d",(q+i*c+j));

}

}

}

display(int *q,int r,int c)

{int i,j;

for(i=0;i

{

printf("\n");

for(j=0;j

{

printf("%d\t",*(q+i*c+j));

}

}

}

prod(int *p,int *q,int *z,int r1,int c2)

{int i,j,k;

for(i=0;i

{

for(j=0;j

{

*(z+i*c2+j)=0;

for(k=0;k

{

*(z+i*c2+j)+=*(p+k*2+j)*(*(q+i*c2+k));

}

}

}

}

//Designed by Asjad Farrukh.......

Answer 2

Matrix multiplication using pointers1. Why use it?Hi, so I've been looking for this answer myself and because it was not created at that time I've decided to do it.

Why use the multiplication by pointers other than normal multiplication by using 2 dimensional arrays (e.g. array[number rows][number columns] ) ? The point is when to use it. When calculating small matrices like matrix 3x3 or matrix 10x10 it is normally possible to use the second way (i think its easier) however, when asked to multiply a matrix of 1024 x 768 its best to use the pointer version, because when using the second way without the use of pointer, a computer has to do a lot more operations than with the pointer version, therefore it will take longer. Time is money and this is why pointers are used in this algorithm.

2. CompilingThe code i have made was tested under GNU C compiler using Code Blocks program. It should be compatible with bloodshed DevCPP program. The reason I am writing this is because MS Visual Studio might pop up a few errors. Maybe because of declarations that Visual Studio compiler won't accept. 3. The whole program//Includes for I/O and Standard Library

#include

#include

//Define functions that will be used in the program

void multiplyMatrices();

void getRowColumn(int *row, int *col, char *matrix);

int *createMatrix(int *row, int *col);

void getMatrixValues(int *source, int row, int col, char *name);

int *destroyMatrix(int *matrix);

void printMatrix(const int *source, int row, int col);

//Start of main

int main()

{

//Call multiplyMatrices function

multiplyMatrices();

//End main

return(0);

//End of main

}

//Start of multiplyMatrices function

void multiplyMatrices()

{

//Declare variables

int oneRow, oneCol, twoRow, twoCol, i, j, k;

//Call getRowColumn to ask user for the matrix size for both matrices

getRowColumn(&oneRow, &oneCol, "Matrix 1");

getRowColumn(&twoRow, &twoCol, "Matrix 2");

//The number of columns in oneMatrix must equal the number of rows in twoMatrix

if(oneCol != twoRow)

{

printf("The number of columns in the first matrix must equal the number of rows in the second matrix.\n");

exit(EXIT_FAILURE);

}

//Create the arrays in the heap memory

int *oneMatrix = createMatrix(&oneRow, &oneCol);

int *twoMatrix = createMatrix(&twoRow, &twoCol);

int *multipliedMatrix = createMatrix(&oneRow, &twoCol);

//Declare pointer variables to store the initial locations of my arrays for later use

int *initialOneMatrix, *initialTwoMatrix, *initialMultipliedMatrix;

initialOneMatrix = oneMatrix;

initialTwoMatrix = twoMatrix;

initialMultipliedMatrix = multipliedMatrix;

//Ask user for the values of each matrix

getMatrixValues(oneMatrix, oneRow, oneCol, "Matrix 1");

getMatrixValues(twoMatrix, twoRow, twoCol, "Matrix 2");

//Multiply the matrices (took me like 5 hours in the debugger to figure out how to arrange these loops lol)

//A for loop while i is less than oneRow(number of rows in first matrix)

for(i = 0; i < oneRow; i++)

{

//A for loop while j is less than twoCol

for(j = 0; j < twoCol; j++)

{

//Increment the address of oneMatrix by its number of columns multiplied by i

oneMatrix += (oneCol * i);

//Increment the address of twoMatrix by j

twoMatrix += j;

//A for loop while k is less than oneCol

for(k = 0; k < oneCol; k++)

{

//Multiply the current entries of the matracies and add the answer to the current entry for the multiplied matrix

*multipliedMatrix += *oneMatrix * *twoMatrix;

//Increment oneMatrix by 1

oneMatrix++;

//Increment twoMatrix by the number of its columns

twoMatrix += twoCol;

}

//Increment multipliedMatrix

multipliedMatrix++;

//"Rewind" oneMatrix to its original address

oneMatrix = initialOneMatrix;

//"Rewind" twoMatrix to its original address

twoMatrix = initialTwoMatrix;

}

}

//"Rewind" multipliedMatrix to its original address

multipliedMatrix = initialMultipliedMatrix;

//Newline to make it pretty

printf("\n");

//Call printMatrix function to print oneMatrix

printMatrix(oneMatrix, oneRow, oneCol);

//Newline, multiplication symbol, and two more newlines to make it pretty

printf("\n*\n\n");

//Call printMatrix function to print twoMatrix

printMatrix(twoMatrix, twoRow, twoCol);

//Newline, equal sign, and two more newlines to make it pretty

printf("\n=\n\n");

//Call printMatrix function to print multipliedMatrix

printMatrix(multipliedMatrix, oneRow, twoCol);

//Call destroyMatrix function to clear clear all of the matrices from memory

destroyMatrix(oneMatrix);

destroyMatrix(twoMatrix);

destroyMatrix(multipliedMatrix);

return;

//End of multiplyMatrices

}

//Start of getRowColumn function

void getRowColumn(int *row, int *col, char *matrix)

{

//Ask user how many rows for the specified matrix

printf("Please enter the number of rows for %s\n", matrix);

//Set variable 'row' to what the user input

scanf("%d", row);

//Ask user how many columns for the specified array

printf("Please enter the number of columns for %s\n", matrix);

//Set variable 'col' to what the user input

scanf("%d", col);

//End of getRowColumn

}

//Start of createMatrix function

int *createMatrix(int *row, int *col)

{

//Initialize the new matrix in the heap memory using calloc with row times col for an argument and using sizeof to let calloc know the size of int

int *newMatrix = calloc(*row * *col, sizeof(int));

//Check if newMatrix is nonexistent, if so the memory was unable to allocate and exit the program

if(!newMatrix)

{

printf("Unable to allocate memory.\n");

exit(EXIT_FAILURE);

}

//Return the newMatrix to where the function was called

return(newMatrix);

//End of createMatrix

}

//Start of getMatrixValues

void getMatrixValues(int *source, int row, int col, char *name)

{

//Declare counting variables for the for loops

int i, j;

//For loop to cycle through the rows

for(i = 0; i < row; i++)

{

//For loop to cycle through the columns

for(j = 0; j < col; j++)

{

//Ask user for a value for the specified entry

printf("Enter the value for %d %d for %s\n", i, j, name);

//Set source to what the user input, then increment source by 1

scanf("%d", source++);

}

}

//End of getMatrixValues

}

//Start of destroyMatrix function

int *destroyMatrix(int *matrix)

{

//Check if matrix exists

if(matrix)

{

//Function to free the matrix from memory

free(matrix);

}

return(NULL);

//End of destroyMatrix

}

//Start of printMatrix function

void printMatrix(const int *source, int row, int col)

{

//Declare counting variables for the for loops

int i, j;

//Cycle through the rows

for(i = 0; i < row; i++)

{

//Print beginning "side" to the matrix

printf("|");

//Cycle through the columns

for(j = 0; j < col; j++)

{

//Print the specified matrix entry

printf("%5d", *source++);

}

//Print an ending "side" to the matrix with a newline

printf("|\n");

}

//End of printMatrix

}

I realize answers.com does not format indents, so if you paste this in a reasonably good source code editor (xcode does this) it will auto indent and such.

Answer 3

#include<stdio.h>

#include<conio.h>

void accept(int[][10],int,int);

void mul(int[][10],int[][10],int[][10],int,int,int);

void disp(int[][10],int,int);

void main()

{int a[10][10],b[10][10],c[10][10],r1,c1,r2,c2;

clrscr();

printf("\n enter rows and col of 1st matrix");

scanf("%d%d",&r1,&c1);

printf("\n enter rows and col of 2nd matrix");

scanf("%d%d",&r2,&c2);

if(c1==r2)

{printf("\n enter elements of 1st matrix");

accept(a,r1,c1);

disp(a,r1,c1);

printf("\n enter elements of 2nd matrix");

accept(b,r2,c2);

disp(b,r2,c2);

mul(a,b,c,r1,c2,r2);

disp(c,r1,c2);

}

void accept(int x[][10],i,j)

printf("\n input elements of first matrix");

for(i=0;i< r;i++) {

for(j=0;j< c;j++)

{

scanf("%d",&x[i][j]);

}

}

void mul(int a[][10],int b[][10],int c[][10],int r1,c2,r2)

for(i=0;i< m;i++) {

for(j=0;j< q;j++) {

c[i][j] = 0;

for(k=0;k< n;k++) {

c[i][j] = c[i][j] + a[i][k] * b[k][j];

}

}

}

void disp(int x[][10],r,c)

for(i=0;i<r1;i++)

{for(j=0;j<c2;j++)

{printf("%5d \t",c[i][j]);

}

printf("\n");

}

}

Answer 4

write a program for multiplication of two 3x3 matrix using pointer

----------------------------------------------------------------------------------

#include<conio.h>

#include<stdio.h>

#include<alloc.h>

void main()

{

int (*a)[10],(*b)[10],(*c)[10],m,n,p,q,i,j,k;

clrscr();

printf("Rows and coloumns of 1 st matrix:");

scanf("%d%d",&m,&n);

printf("Rows and coloumns of 2 nd matrix:");

scanf("%d%d",&p,&q);

if(n!=p)

{

printf("Not possible");

}

else

{

a=(int*)malloc(m*n*sizeof(int));

b=(int*)malloc(p*q*sizeof(int));

c=(int*)malloc(n*p*sizeof(int));

printf("Enter first matrix:");

for(i=0;i<m;i++)

for(j=0;j<n;j++)

scanf("%d",(*(a+i)+j));

printf("Enter second matrix:\n");

for(i=0;i<p;i++)

for(j=0;j<q;j++)

scanf("%d",(*(b+i)+j));

printf("First matrix is:\n");

for(i=0;i<m;i++)

{

printf("\n");

for(j=0;j<n;j++)

printf("%d\t",*(*(a+i)+j));

}

printf("\nSecond matrix is:\n");

for(i=0;i<p;i++)

{

printf("\n");

for(j=0;j<q;j++)

printf("%d\t",*(*(b+i)+j));

}

for(i=0;i<m;i++)

{

for(j=0;j<q;j++)

{

*(*(c+i)+j)=0;

for(k=0;k<n;k++)

*(*(c+i)+j)+=*(*(a+i)+k)*(*(*(b+k)+j));

}

}

printf("\nProduct=\n");

for(i=0;i<m;i++)

{

printf("\n");

for(j=0;j<q;j++)

printf("%d\t",*(*(c+i)+j));

}

}

getch();

}

Answer 5

#include<stdio.h>

#include<conio.h>

void main()

{

int a,b,sum;

clrscr();

printf("enter the two numbers");

scanf("%d%d",&a,&b);

sum=a+b;

printf("sum =%d");

getch();

}

Answer 6

#include<stdio.h>

main()

{

int a[3][3],b[3][3],c[3][3];

int i,j,k;

printf("enter the elements in A matrix:\n");

for(i=0;i<=2;i++)

{

for(j=0;j<=2;j++)

{

scanf("%d",&a[i][j]);

}

}

printf("enter b matrix:\n");

for(i=0;i<=2;i++)

{

for(j=0;j<=2;j++)

{

scanf("%d",&b[i][j]);

}

}

for(i=0;i<=2;i++)

{

printf("\n");

for(j=0;j<=2;j++)

{

c[i][j]=0;

for(k=0;k<=2;k++)

{

c[i][j] = c[i][j]+a[i][k] * b[k][j];

}

}

}

printf("multiplication matrix is:\n");

for(i=0;i<=2;i++)

{

for(j=0;j<=2;j++)

{

printf("%d\t",c[i][j]);

}

printf("\n");

}

}

Answer 7

int* add(int *i,int *j)

{

int *result;

*result=(*i) + (*j);

return result;

}

main()

{

int *i,*j,,*res;

*i=3;

*j=5;

res=add(i,j);

printf("%d",*res);

}