Reading data from file and performing matrix multiplication

[veenatapaswi]

hii.. i am new to c++ am trying to perform a matrix multiplication taking data from a file.But am unable to get the multiplication part.Someone plz help me to fix this.

#include <iostream>
#include <fstream>
#include <array>
#include <sstream>
#include <string>
#include <stdio.h>

int rowA=0;
int colA=0;
int i=0,j=0,k=0;
using namespace std;

int main()
{
string line;
ifstream myfile;
int x;
int y;
int arrayA[100][100] = {{0}};
int arrayB[100][100] = {{0}};
int arrayC[100][100] = {{0}};
myfile.open("numeric.txt");
if(myfile.fail())
{
cerr<<"file does not exist";

}
cout<<"\n"<<endl;
while(myfile.good())
{
while(getline(myfile,line))
{
istringstream stream(line);
colA=0;
while(stream >> x)
{
arrayA[rowA][colA]=x;
colA ++;
}
rowA ++;
}

for(int i=0;i<rowA;i++)
{
for(int j=0;j<colA;j++)
{
cout<<arrayA[i][j]<< " " ;
}
cout<<endl;
}
cout<<"\n"<<endl;
}
cout<<"first Matrix"<<endl;
	for(i=1;i<=3;i++)
	{
		for(j=0;j<3;j++)
		{
		 
			cout<<arrayA[i][j]<<" ";
		}
		cout<<endl;
	}


	cout<<"Second Matrix"<<endl;
	for(i=1;i<=3;i++)
	{
		for(j=1;j<=3;j++)
		{
                        arrayB[i][j] = arrayA[i][j];
                        cout<<arrayB[i][j]<<" ";
		}
		cout<<endl;
	}

	for(i=0;i<3;i++)
	{
		for(j=0;j<3;j++)
		{
			
			for(k=0;k<3;k++)
			{
				arrayC[i][j]+=arrayA[i][k]*arrayB[k][j];
			}
                 }
	}
	cout<<"Multiplication Result"<<endl;
	for(i=0;i<3;i++)
	{
		for(j=0;j<3;j++)
		{
			cout<<arrayC[i][j]<<" ";
		}
		cout<<endl;
	}
	
return 0;
}

[lastchance]

You copied the matrix multiplication from elsewhere, so that part of the code is fine. The rest of it is bizarre.

Why are you reading your two-dimensional arrays of numbers into one-dimensional arrays of arrays of strings (lines 12-14)?

For file input (and output) see http://www.cplusplus.com/doc/tutorial/files/
For use of arrays see http://www.cplusplus.com/doc/tutorial/arrays/

[veenatapaswi]

Thanku for your reply..I have made changes to my code...Can you plz tell me what is the issue with the code...

#include <iostream>
#include <fstream>
#include <array>
#include <sstream>
#include <string>
#include <stdio.h>

int rowA=0;
int colA=0;
int i=0,j=0,k=0;
using namespace std;

int main()
{
string line;
ifstream myfile;
int x;
int y;
int arrayA[100][100] = {{0}};
int arrayB[100][100] = {{0}};
int arrayC[100][100] = {{0}};
int arrayD[100][100] = {{0}};
myfile.open("numeric.txt");
if(myfile.fail())
{
cerr<<"file does not exist";
}
cout<<"\n"<<endl;
while(myfile.good())
{
while(getline(myfile,line))
{
istringstream stream(line);
colA=0;
while(stream >> x)
{
arrayA[rowA][colA]=x;
colA ++;
}
rowA ++;
}

for(int i=0;i<rowA;i++)
{
for(int j=0;j<colA;j++)
{
cout<<arrayA[i][j]<< " " ;
// arrayB[i][j] = arrayA[i][j];
// cout<<endl;
// cout<<arrayB[i][j]<< " " ;
}
cout<<endl;
}
cout<<"\n"<<endl;
}
cout<<"first Matrix"<<endl;
for(i=1;i<=3;i++)
{
for(j=0;j<3;j++)
{
// arrayB[i][j] = arrayA[i][j];
cout<<arrayA[i][j]<<" ";
}
cout<<endl;
}


cout<<"Second Matrix"<<endl;
for(i=3;i<6;i++)
{
for(j=3;j<6;j++)
{
// arrayC[i][j] = arrayA[i][j];
cout<<arrayA[i][j]<<" ";
}
cout<<endl;
}
cout<<"Multiplication Result"<<endl;
for(i=0;i<3;i++)
{
for(j=0;j<3;j++)
{
int sum = 0;
for(k=0;k<3;k++)
{
sum=sum+arrayA[i][k]*arrayA[k][j];
}
arrayD[i][j]=sum;
}
}
// cout<<"Multiplication Result"<<endl;
for(i=0;i<3;i++)
{
for(j=0;j<3;j++)
{
cout<<arrayD[i][j]<<" ";
}
cout<<endl;
}

return 0;
}