Matrix Problem

Hey Guys,

I need your expertise. Please help me.

In the following program, 2 matrices and given values and then displayed. The program works fine but I really can't understand how it works.

#include <stdio.h>
#include <stdlib.h>

void getmat(int a[50][50],int n)
{
    int i,j;
    for(i=0;i<n;i++)
        for(j=0;j<n;j++)
            scanf("%d",&a[i][j]);
}

void printmat(int a[50][50],int n)
{
    int i,j;
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
            printf("%d\t",a[i][j]);
        }
        printf("\n");
    }
}

int main()
{
    int a[50][50],b[50][50];
    int n;
    printf("\nEnter Limit : ");
    scanf("%d",&n);
    getmat(a,n);
    getmat(b,n);
    printmat(a,n);
    printf("\n");
    printmat(b,n);
    return 0;
}

I have used VOID functions that technically doesnot return any values. But this program works flawlessly!! It gets the values that I input and prints them seperately. I don't get the flow of the program. Without any return statements how the Matrices A and B got their respective values remain a mystery.

I would be so grateful if you would be so kind to clear me off this doubt.

Thanks,
Ladis

[deceptikon]

The trick is that arrays in C are passed by simulated reference. The syntax you're using obscures it a bit, but these three declarations are functionally identical:

void getmat(int a[50][50],int n);
void getmat(int a[][50],int n);
void getmat(int (*a)[50],int n);

So an array is actually passed as a pointer to the first element, which is how you simulate pass by reference in C. And that's why when you scanf into a[i][j], it actually modifies the original array passed in from main.

The weirdness of arrays in C makes a lot more sense when you have a good handle on pointers.

Thanks a lot deceptikon

And would you please tell me how to use the return statements for returning Matrices

For example using getmat() function as an integer function

Thanks,
Ladis

[deceptikon]

And would you please tell me how to use the return statements for returning Matrices

Stop using arrays and switch to vectors (or a matrix class), that's how you do it:

vector<vector<int>> func();

There are some things that array types simply aren't suited for, and this is one of them.