symmetric matrix?

[number87]

erm im trying to create a function to test if an array/matrix is symmetrical
that is for example a[i,j] = a[j,i]
i think i got the symmetrical test function correct....just that i dont know where to put that if-else statement. it just doesnt seem to fit anywhere in my codes.

#include <iostream>
using namespace std;

const int MAXROW = 10;
const int MAXCOL = 10;

int main()
{
  srand(time(NULL));
  
  int a [MAXROW][MAXCOL];
 
  for (int row = 0; row < MAXROW; row++)
  {  
    for (int col = 0; col < MAXCOL; col++)
      {
             a[row][col] = rand () % 10;
             cout << a[row][col] << "\t";                     
      }
    cout << endl;
    
    if (a[row][col] == a[col][row])
         cout << "Symmetric" << endl;
    else
         cout << "Not symmetric" << endl;
  }       
return 0;
}

[Ancient Dragon]

Populating the matrix with random numbers will almost never give you a semmatric matrix. In order to test your program you will have to hard-code the matrix with known values like this

You have to create two nested loops to test each value, like this:

for(int i = 0; i < MAXROW; ++i)
{
   for(int j = 0; i < MAXCOL; ++j)
    {
          // put test here
    }
}

[number87]

hmm i tried your suggestion but it gives me some strange results...i got something like this

4 symmetric
9 non symmetric
1 non symmetric
0 symmetric
etc
etc

this is what i got after ur suggestion

#include <iostream>
using namespace std;

const int MAXROW = 10;
const int MAXCOL = 10;

int main()
{
  srand(time(NULL));
  
  int a [MAXROW][MAXCOL];
 
  for (int row = 0; row < MAXROW; row++)
  {  
    for (int col = 0; col < MAXCOL; col++)
      {
             a[row][col] = rand () % 10;
             cout << a[row][col] << "\t";                     
            
            if (a[row][col] == a[col][row])
                 cout << "Symmetric" << endl;
            else
                 cout << "Not symmetric" << endl;      
      }
    cout << endl;


  }       
return 0;
}

[Ancient Dragon]

You can't make the test until after the matrix has been filled in. So move lines 20-23 down after line 25 and start a new set of nested loops.

And as I said before you can't make this test using rand() to populate the array as you are doing on line 17 because you will almost never get a symmetric matrix that way.

[number87]

ohh..i get what u mean now:icon_idea: