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C++ Matrix Multiplication

Hey guys, I am incredibly new to c++ and need a little help on a matrix multiplyer program...

#include <iomanip> 
#include <iostream>
using namespace std;
int main()
{

int **mat1;
int **mat2;
int **result;
int row,col;

cout<<"Please enter row/col"<<endl;
cin>>row>>col;

mat1 = new int *[row];
mat2 = new int *[row];
result = new int *[row];
int k,i,j;

for (k=0; i<row; k++)
    mat1[k] = new int[col];
    mat2[k] = new int[col];
    result[k] = new int[col];
    
              for (i=0; i<row; i++)
                  for (j=0; j<col; j++)
                      for (j=0; j<row; j++)
                          for(i=0; i<col; i++)
                          result[i][k] += (mat1 [i][k] * mat2[k][j]);

cout<<setw(4)<<result[i][k];

I know obviously that I need 3 arrays, 1 and 2 to multiply and 3 to store the result. I'm just really bad at reading nested loops... and c++ in general. any help would be appreciated.

Etniespr101

Newbie Poster

9 posts since Oct 2007

Reputation Points: 10

Solved Threads: 0

4 Years Ago

Where do you input values into the arrays, prior to running the multiply code?

It might run as written, but it will surely produce a bunch of garbage output.

Salem

Posting Sage

Team Colleague

11,531 posts since Dec 2005

Reputation Points: 5,862

Solved Threads: 953

4 Years Ago

hey thx for the reply. I input values into the the arrays at the beginning where the user inputs. im guessing your saying that my arrays have no value as of right now because i'm not giving it anything... im confused..

Etniespr101

Newbie Poster

9 posts since Oct 2007

Reputation Points: 10

Solved Threads: 0

4 Years Ago

Where do you input values into the arrays, prior to running the multiply code?

It might run as written, but it will surely produce a bunch of garbage output.

i added a little bit...

#include <iomanip> 
#include <iostream>
using namespace std;
int main()
{

int **mat1;
int **mat2;
int **result;
int row,col;

cout<<"Please enter row/col"<<endl;
cin>>row>>col;

mat1 = new int *[row];
mat2 = new int *[row];
result = new int *[row];
int k,i,j;

for (k=0; k<row; k++)
    mat1[k] = new int[col];
    mat2[k] = new int[col];
    result[k] = new int[col];
    
              for (i=0; i<row; i++)
                 for (j=0; j<col; j++)
                    mat1[k][i] = k + i;
                      for (j=0; j<row; j++)
                          mat2[i][k] = j + k;
                                     for(i=0; i<col; i++)
                                     result[i][k] += (mat1 [i][k] * mat2[k][j]);

cout<<setw(4)<<result[i][k];

Etniespr101

Newbie Poster

9 posts since Oct 2007

Reputation Points: 10

Solved Threads: 0

3 Years Ago

#include <iostream.h>
#include <conio.h>

void getResult(double a[100][100], double b[100][100], double mVal, double pVal, double nVal)
{
		for(int i=0; i<mVal; i++)
   	{
   		for(int j=0; j<pVal; j++)
      	{
      		int res = 0;
      		for(int k=0; k<nVal; k++)
         		res += a[i][k]*b[k][j];
            	cout<<res<<"\t";
      	}
      	cout<<endl;
   	}
}

int main()
{
double a[100][100];
double b[100][100];
double mValue;
double nValue;
double pValue;
char ans;
char response;

do{
cout<<"\t\tM A T R I X   M U L T I P L I C A T I O N\n\n\n";
cout<<"This program will compute the product of two matrices.\n";
cout<<"\nAmxn and Bnxp, \n\nwhere m and p less than or equal to n (m, p <= n )\n";
cout<<"To use the program, just follow what the program asks.";
cout<<"\n\n\nNOTE:\n\tTo type the value or entries of a matrix just follow this; ";
cout<<"\n\n\t  1. You can type like this 1 2 3 4 5 6 . . . n\n";
cout<<"\n\t  2. or you can type like this \n\n\t    a11 a12 . . . a1n\n\t    a21 a22 . . . a2n \n\t    . . .";
cout<<"\n\t    .\n\t    .\n\t    .\n\t    am1 am2 . . . amxn or nxp\n\n";
cout<<"\nMAXIMUM DIMENSIONS = 10 X 10 (RECOMMENDED)\n";
cout<<"\nYOU CAN ALSO USE UP TO 100 X 100 DIMENSIONS\n\n\n";
cout<<"Want to use the program? : \n";
cout<<"type 'y' to continue and press any key to EXIT then press ENTER: ";
cin>>response;

	if((response=='y')||(response=='Y'))
   {
 		cout<<"\n\nEnter the value of m: ";
		cin>>mValue;
      while(mValue<=0)
   	{
      	cout<<"\n\nINCORRECT dimension(s), no negative or zero dimension(s) in a matrix\n";
   		cout<<"\nEnter the value of m greater than "<<mValue<<" : ";
   		cin>>mValue;
   	}
		cout<<"\nEnter the value of p: ";
		cin>>pValue;
      while(pValue<=0)
   	{
      	cout<<"\n\nINCORRECT dimension(s), no negative or zero dimension(s) in a matrix\n";
   		cout<<"\nEnter the value of p greater than "<<pValue<<" : ";
   		cin>>pValue;
   	}
		cout<<"\nEnter the value of n: ";
		cin>>nValue;
      while(nValue<0)
   	{  nValue = 0;
   		cout<<"\nEnter the value of n greater than "<<nValue<<" and less than "<<pValue<<" or "<<mValue<<" : ";
      	cin>>nValue;
   	}
      while((nValue>mValue)||(nValue>pValue))
   	{
         if(mValue>pValue)
         {
 				cout<<"\nERROR:\n\tValue of n must be less than or equal to "<<pValue<<"\n\n";
 				cout<<"Enter the value of n: ";
				cin>>nValue;
         }
         else
         {
         	cout<<"\nERROR:\n\tValue of n must be less than or equal to "<<mValue<<"\n\n";
 				cout<<"Enter the value of n: ";
				cin>>nValue;
         }
 		}


				cout<<"\n\nEnter a matrix with this dimension(s) A "<<mValue<<"x"<<nValue<<": \n";
				cout<<"\n\nType "<<(nValue*mValue)<<" entries for matrix A: \n\n";

            for(int i=0; i<mValue; i++)
   			{
      			for(int j=0; j<nValue; j++)
      				cin>>a[i][j];
   			}

				cout<<"\nThe value of matrix A that you have entered: \n\n";
   			for(int i=0; i<mValue; i++)
   			{
      	  		for(int j=0; j<nValue; j++)
      				cout<<a[i][j]<<"\t";
         			cout<<endl;
   			}
				cout<<"\n\nEnter a matrix with this dimension(s) B "<<nValue<<"x"<<pValue<<": \n";
				cout<<"\n\nType "<<(nValue*pValue)<<" entries for matrix B: \n\n";

				for(int i=0; i<nValue; i++)
   			{
   				for(int j=0; j<pValue; j++)
      				cin>>b[i][j];
   			}
   			cout<<"\nThe value of matrix B that you have entered: \n\n";
   			for(int i=0; i<nValue; i++)
   			{
   				for(int j=0; j<pValue; j++)
    		  		cout<<b[i][j]<<"\t";
   		      	cout<<endl;
   			}
				cout<<"\n\n\nThe PRODUCT is: \n\n";
   			getResult(a,b,mValue,pValue,nValue);
      }
      else
      	break;

   cout<<"\n\nTry again? \n\nType y to try again and press any key to stop then press ENTER. : ";
   cin>>ans;
}while((ans=='y')||(ans=='Y'));
cout<<"\n\n\nThanks for using this program.";
cout<<"\n\nProgrammer:\n\n\tMR. MOHAMMAD FAIDZ UY UBPON";
cout<<"\n\tBS COMPUTER SCIENCE \n\tMindanao State University\n\tCollege of Information Technology";

cin.get();
cin.get();
return 0;
}

mfubpon

Newbie Poster

1 post since Dec 2008

Reputation Points: 10

Solved Threads: 1

3 Years Ago

please use code tags

daviddoria

Posting Virtuoso

1,996 posts since Feb 2008

Reputation Points: 437

Solved Threads: 204

3 Years Ago

And why are you posting in a thread last posted to in October 2007?

Murtan

Practically a Master Poster

671 posts since May 2008

Reputation Points: 344

Solved Threads: 116

2 Years Ago

Show Comments

-3

Just checking to see if how Quick Reply works.
I'm new to DaniWeb. :P

JProgrammer

Newbie Poster

1 post since Nov 2009

Reputation Points: 6

Solved Threads: 1

2 Years Ago

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Hey guys, I am incredibly new to c++ and need a little help on a matrix multiplyer program...
#include <iomanip> 
#include <iostream>
using namespace std;
int main()
{

int **mat1;
int **mat2;
int **result;
int row,col;

cout<<"Please enter row/col"<<endl;
cin>>row>>col;

mat1 = new int *[row];
mat2 = new int *[row];
result = new int *[row];
int k,i,j;

for (k=0; i<row; k++)
    mat1[k] = new int[col];
    mat2[k] = new int[col];
    result[k] = new int[col];
    
              for (i=0; i<row; i++)
                  for (j=0; j<col; j++)
                      for (j=0; j<row; j++)
                          for(i=0; i<col; i++)
                          result[i][k] += (mat1 [i][k] * mat2[k][j]);

cout<<setw(4)<<result[i][k];
I know obviously that I need 3 arrays, 1 and 2 to multiply and 3 to store the result. I'm just really bad at reading nested loops... and c++ in general. any help would be appreciated.

The problem is that you did not close the bracket so you are getting the errors. Also when I test the program I could only use the integers 1 and 0, is that how it should be? Try it and if still have problems, then reply back.

techboy2099

Newbie Poster

2 posts since Mar 2010

Reputation Points: 10

Solved Threads: 1

2 Years Ago

you need to close the code with the bracket and when I ran the program, I was only able to use the integers 1 and 0. Is that how the program should be? try the program and if any problems reply back.

techboy2099

Newbie Poster

2 posts since Mar 2010

Reputation Points: 10

Solved Threads: 1

2 Years Ago

Try it and if still have problems, then reply back.

It's been over 2.5 years. (S)He has probably solved the problem by now.

Nick Evan

Not a Llama

Moderator

10,112 posts since Oct 2006

Reputation Points: 4,142

Solved Threads: 403

2 Years Ago

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Where do you input values into the arrays, prior to running the multiply code?

It might run as written, but it will surely produce a bunch of garbage output.

plz send a program in C++ by using array matix multipication

Sardar Noman

Newbie Poster

1 post since May 2010

Reputation Points: 9

Solved Threads: 0

2 Years Ago

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