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Still can't get the function right with a matrix

Billy George (9)
So I read the function 1 and 2 on the forum and kinda understand it. But I cannot apply it to when it comes to matrices. The homework problem wants me to write functions on multiplying and adding functions. I got the math part right as you can see on line 36 and 63.

So now I am trying to write function where I can add the two first, but I keep coming up with errors.

My function is line 7 and my recall of that function is line 35. I've tried different ways of writing it and keep getting errors. Please help with this one function and so I can write the other function for multiplying them.

Thank you!



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#include <cmath>
#include <iostream>

using namespace std;


int addMatrix(int MA[3][3], int MB[3][3]){
     int MC[3][3];
     for (int i=0;i<=2;i++){
         for (int j=0;j<=2;j++) {
             MC[i][j]=MA[i][j]+MB[i][j];
             }
             }
         return MC[3][3];
         }

int main(int argc, char *argv[])
{
   
   int matrixA[3][3], matrixB[3][3], matrixC[3][3], multMatrix[3][3];

   //Enter info for the first matrix
   cout<<"\tEnter the values for Matrix A in 3 by 3: "<<endl;
   for (int i=0;i<=2;i++){
         for (int j=0;j<=2;j++) {
             cin>>matrixA[i][j];
             }}

   //Enter the info for the second matrix
   cout<<"\n\nEnter the values for Matrix B in 3 by 3: "<<endl;
   for (int i=0;i<=2;i++){
         for (int j=0;j<=2;j++) {
             cin>>matrixB[i][j];
             }}
   matrixC[3][3]= addMatrix(matrixA[3][3], matrixB[3][3]);
   //This will add the two matrices together
  //   for (int i=0;i<=2;i++){
    //     for (int j=0;j<=2;j++) {
      //       matrixC[i][j]=matrixA[i][j]+matrixB[i][j];
        //     }
          //   }
             
   //Displays the matrices
   cout<<"\n\nMatrix A and Matrix B\n\n";
   
   cout<<matrixA[0][0]<<"\t"<<matrixA[0][1]<<"\t"<<matrixA[0][2]<<"\n";
   cout<<matrixA[1][0]<<"\t"<<matrixA[1][1]<<"\t"<<matrixA[1][2]<<"\n";
   cout<<matrixA[2][0]<<"\t"<<matrixA[2][1]<<"\t"<<matrixA[2][2]<<"\n";
   cout<<"and\n\n";
   cout<<matrixB[0][0]<<"\t"<<matrixB[0][1]<<"\t"<<matrixB[0][2]<<"\n";
   cout<<matrixB[1][0]<<"\t"<<matrixB[1][1]<<"\t"<<matrixB[1][2]<<"\n";
   cout<<matrixB[2][0]<<"\t"<<matrixB[2][1]<<"\t"<<matrixB[2][2]<<"\n";
  
  
   //Displays the addition of the matrices
   cout<<"\n\nThe adding of the two matrice is\n\n";
   
   cout<<matrixC[0][0]<<"\t"<<matrixC[0][1]<<"\t"<<matrixC[0][2]<<"\n";
   cout<<matrixC[1][0]<<"\t"<<matrixC[1][1]<<"\t"<<matrixC[1][2]<<"\n";
   cout<<matrixC[2][0]<<"\t"<<matrixC[2][1]<<"\t"<<matrixC[2][2]<<"\n";
  
  //Mulitplying the matrices together
  for (int i=0;i<=2;i++){
         for (int j=0;j<=2;j++) {
             multMatrix[i][j]=0;
             for (int k=0; k<=2;k++){
                 multMatrix[i][j]+=matrixA[i][k]*matrixB[k][j];
                 }
                 }
                 }
                 
    //Displays the Product of the matrices
   cout<<"\n\nThe product of the two matrice is\n\n";
   
   cout<<multMatrix[0][0]<<"\t"<<multMatrix[0][1]<<"\t"<<multMatrix[0][2]<<"\n";
   cout<<multMatrix[1][0]<<"\t"<<multMatrix[1][1]<<"\t"<<multMatrix[1][2]<<"\n";
   cout<<multMatrix[2][0]<<"\t"<<multMatrix[2][1]<<"\t"<<multMatrix[2][2]<<"\n";
               
                 
  
  
   system("PAUSE");
   return EXIT_SUCCESS;
}
MiiNiPaa (8886)
Arrays in C++ are basically pointers. In your function:
Line 7: allocating memory for array;
Line 14: Returning pointer to MC[0][0]
Line 15: MC goes out of scope and is deallocated.

Posiible solutions:
a) Dinamically allocate your array.
b) Pass array you, want write result to, to your addMatrix function.
voidmainvoid (10)
MiinIPaa is correct. You need to pass the result array to AddMatrix Function.
I have fixed your program.
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#include <cmath>
#include <iostream>
#include <windows.h>

using namespace std;

void addMatrix(int MC[3][3],int MA[3][3], int MB[3][3])
    {
     for (int i=0;i<=2;i++){
         for (int j=0;j<=2;j++) {
             MC[i][j]=MA[i][j]+MB[i][j];
             }
             }
         }

int main(int argc, char *argv[])
{

   int matrixA[3][3], matrixB[3][3], matrixC[3][3], multMatrix[3][3];

   //Enter info for the first matrix
   cout<<"\tEnter the values for Matrix A in 3 by 3: "<<endl;
   for (int i=0;i<=2;i++){
         for (int j=0;j<=2;j++) {
             cin>>matrixA[i][j];
             }}

   //Enter the info for the second matrix
   cout<<"\n\nEnter the values for Matrix B in 3 by 3: "<<endl;
   for (int i=0;i<=2;i++){
         for (int j=0;j<=2;j++) {
             cin>>matrixB[i][j];
             }}
    addMatrix(matrixC,matrixA,matrixB);
   //This will add the two matrices together
  //   for (int i=0;i<=2;i++){
    //     for (int j=0;j<=2;j++) {
      //       matrixC[i][j]=matrixA[i][j]+matrixB[i][j];
        //     }
          //   }

   //Displays the matrices
   cout<<"\n\nMatrix A and Matrix B\n\n";

   cout<<matrixA[0][0]<<"\t"<<matrixA[0][1]<<"\t"<<matrixA[0][2]<<"\n";
   cout<<matrixA[1][0]<<"\t"<<matrixA[1][1]<<"\t"<<matrixA[1][2]<<"\n";
   cout<<matrixA[2][0]<<"\t"<<matrixA[2][1]<<"\t"<<matrixA[2][2]<<"\n";
   cout<<"and\n\n";
   cout<<matrixB[0][0]<<"\t"<<matrixB[0][1]<<"\t"<<matrixB[0][2]<<"\n";
   cout<<matrixB[1][0]<<"\t"<<matrixB[1][1]<<"\t"<<matrixB[1][2]<<"\n";
   cout<<matrixB[2][0]<<"\t"<<matrixB[2][1]<<"\t"<<matrixB[2][2]<<"\n";


   //Displays the addition of the matrices
   cout<<"\n\nThe adding of the two matrice is\n\n";

   cout<<matrixC[0][0]<<"\t"<<matrixC[0][1]<<"\t"<<matrixC[0][2]<<"\n";
   cout<<matrixC[1][0]<<"\t"<<matrixC[1][1]<<"\t"<<matrixC[1][2]<<"\n";
   cout<<matrixC[2][0]<<"\t"<<matrixC[2][1]<<"\t"<<matrixC[2][2]<<"\n";

  //Mulitplying the matrices together
  for (int i=0;i<=2;i++){
         for (int j=0;j<=2;j++) {
             multMatrix[i][j]=0;
             for (int k=0; k<=2;k++){
                 multMatrix[i][j]+=matrixA[i][k]*matrixB[k][j];
                 }
                 }
                 }

    //Displays the Product of the matrices
   cout<<"\n\nThe product of the two matrice is\n\n";

   cout<<multMatrix[0][0]<<"\t"<<multMatrix[0][1]<<"\t"<<multMatrix[0][2]<<"\n";
   cout<<multMatrix[1][0]<<"\t"<<multMatrix[1][1]<<"\t"<<multMatrix[1][2]<<"\n";
   cout<<multMatrix[2][0]<<"\t"<<multMatrix[2][1]<<"\t"<<multMatrix[2][2]<<"\n";




   system("PAUSE");
   return EXIT_SUCCESS;
}


Compiled and tested on Code Blocks.
Billy George (9)
Thank you very much!

So when I am calling the function for a matrix operation, I don't need to add the [3][3] on line 34. Is that because it was already defined?

But when I am writing a function, I need to specify the [3][3] like on line 7?

Thank you again.
Ownst (3)
I have a very similar problem i'm encountering myself with a solution. I was confused as to if you could just utilize a nested for loop such as

int i, j;
for(i = 0; i < 3; i++)
{
for(j = 0; j < 3; j++)
{

Rather than just as you did with a third for loop with i j k going to less 2.
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