X,Y passing size for the array in C function

I've declared my function where I want to find the minimum from diagonals [0][0] ... [5][5] and [0][5]... [5][0]. I have the algorithm but my problem is with the actual function header.

I have problem with creating the formal arguments for the function. I know that we have to pass at least x[][this] size of array to the function, but I tried various combinations, even

double minimum(int size, double x[][size]){...}

double minimum(double x[][int size]){...}

The first case gives an error when calling:

minimum(10, x[][10])
error: expected expression before ']' token ` 

The second case gives an error in declaration of function:

error: expected expression before 'int' 

Can someone tell what the problem is (or problems are)?

Solution 1:

double minimum(int rowsize,int size, double x[rowsize][size]){...} or simply

double minimum(int rowsize,int size, double x[][size]){...}

So specifying rowsize is optional.

But here I guess it is square size x size so it will be

double minimum(int size, double x[][size]){...}

So you are correct in that.

How to call it?

minimum(10,x)

Solution 2:

If you are dealing with an array of the fixed size 5 then you can declare the function like

double minimum( double x[][5] );

and call it like

minimum( x );

If the size of the array can be changed you can use variable length arrays and declare the function like

double minimum( size_t n, double x[][n] );

of for self-documentation like

double minimum( size_t n, double x[n][n] );

The function can be called like

minimum( 10, x );

or like

minimum( sizeof( x ) / sizeof( *x ), x );