What is going wrong with my multidimentional array function? - c++

Question

here I have a problem. I want to manipulate the following Matrix
Matrix A =
1---------2----------3
4---------5----------6
7---------8----------9
into
7---------8----------9
4---------5----------6
1---------2----------3
#include<iostream>
using namespace std;
void f(int ArrayName, int Size);
int main()
{
int x[3][3]={{1,2,3}, {4, 5,6},{7,8,9}};
f(x, 3);
system("pause");
}
void f(int ArrayName, int Size)
{
int holder;
for(int i=0; i<Size; i++){
for(int j=0; j<Size; j++)
{
holder=ArrayName[i][j];
ArrayName[i][j]=ArrayName[i+2][j+2];
ArrayName[i+2][j+2]=holder;
}
}
for(int k=0; k<Size; k++)
for(int l=0; l<Size; l++)
{
cout<<ArrayName[k][l];
if(l=3) cout<<"\n";
}
}
Errors:
E:\Semester 2\CPrograms\Array2.cpp In function `int main()':
10 E:\Semester 2\CPrograms\Array2.cpp invalid conversion from `int (*)[3][3]' to `int'
10 E:\Semester 2\CPrograms\Array2.cpp initializing argument 1 of `void f(int, int)'
E:\Semester 2\CPrograms\Array2.cpp In function `void f(int, int)':
22 E:\Semester 2\CPrograms\Array2.cpp invalid types `int[int]' for array subscript
(Last error repeated for five times)

Answer 1

All is done before us.:)
You can do quickly the assignment using standard algorithm std::reverse declared in header <algorithm>
For example
#include <iostream>
#include <algorithm>
#include <iterator>
int main()
{
int a[3][3] =
{
{ 1, 2, 3 },
{ 4, 5, 6 },
{ 7, 8, 9 }
};
for ( const auto &row : a )
{
for ( int x : row ) std::cout << x << ' ';
std::cout << std::endl;
}
std::cout << std::endl;
std::reverse( std::begin( a ), std::end( a ) );
for ( const auto &row : a )
{
for ( int x : row ) std::cout << x << ' ';
std::cout << std::endl;
}
return 0;
}
The program output is
1 2 3
4 5 6
7 8 9
7 8 9
4 5 6
1 2 3
As for your code then already this function declaration
void f(int ArrayName, int Size);
is wrong.
The first parameter should be either a reference to the array or a pointer to its first element.
For example
void f( int ( &ArrayName )[3][3] );
or
void f( int ( *ArrayName )[3], int Size );
If you want to write the function yourself then it can look the following way
#include <iostream>
void reverse( int ( *ArrayName )[3], size_t Size )
{
for ( size_t i = 0; i < Size / 2; i++ )
{
for ( size_t j = 0; j < 3; j++ )
{
int tmp = ArrayName[i][j];
ArrayName[i][j] = ArrayName[Size - i - 1][j];
ArrayName[Size - i - 1][j] = tmp;
}
}
}
int main()
{
int a[3][3] =
{
{ 1, 2, 3 },
{ 4, 5, 6 },
{ 7, 8, 9 }
};
for ( const auto &row : a )
{
for ( int x : row ) std::cout << x << ' ';
std::cout << std::endl;
}
std::cout << std::endl;
::reverse( a, 3 );
for ( const auto &row : a )
{
for ( int x : row ) std::cout << x << ' ';
std::cout << std::endl;
}
return 0;
}
The program output will be the same as above.

Answer 2

The prototype and declaration of your function should be :
void f(int ArrayName[][3], int Size)
Modify the code as:
#include<iostream>
using namespace std;
void f(int ArrayName[][3], int Size); //change here
int main()
{
int x[3][3]={{1,2,3}, {4, 5,6},{7,8,9}};
f(x, 3);
system("pause");
}
void f(int ArrayName[][3], int Size) //change here
{
int holder;
for(int i=0; i<Size/2; i++){ //change here
for(int j=0; j<Size; j++)
{
holder=ArrayName[i][j];
ArrayName[i][j]=ArrayName[size-i-1][size-i-1]; //change here
ArrayName[size-i-1][size-i-1]=holder; //change here
}
}

Answer 3

Try the solution in the code below. It uses the matrix as a vector, but has no dimension dependencies in the f() function prototype.
You have some errors in your code:
The array x[][] has to be passed by reference/pointer and not by value, then the function f() has to receive a pointer (or a reference) to int and not an int!
The for-loop scanning the matrix rows doesn't have to be for(int i=0; i<Size; i++), but for(int i=0; i<Size/2; i++). Using i<Size you swaps two times all the rows and then it seems nothing happens!
The following code:
ArrayName[i][j]=ArrayName[i+2][j+2];
ArrayName[i+2][j+2]=holder;
should be:
ArrayName[i][j]=ArrayName[Size-i-1][j];
ArrayName[Size-i-1][j]=holder;
The following code:
if(l=3) cout<<"\n";
l=3 assigns a value, don't do a comparison.
It should be:
if(l==Size-1) cout<<"\n";
#include<iostream>
using namespace std;
void f(int * ArrayName, int Size);
int main()
{
static const int Size=4;
int x[Size][Size];
//Loads the numbes into the matrix
for(int i=0;i<Size;i++)
for(int j=0;j<Size;j++)
x[i][j]=i*Size+j+1;
f(&x[0][0], Size);
}
void f(int *ArrayName, int Size)
{
int holder;
cout << "Input\n";
for(int k=0; k<Size; k++) {
for(int l=0; l<Size; l++)
cout<<ArrayName[k*Size+l]<<" ";
cout << "\n";
}
// Elaborate the matrix
// ----------------------------------------
for(int i=0; i<Size / 2; i++){
for(int j=0; j<Size; j++) {
holder=ArrayName[i*Size+j];
ArrayName[i*Size+j]=ArrayName[(Size-i-1)*Size+j];
ArrayName[(Size-i-1)*Size+j]=holder;
}
}
// ----------------------------------------
cout << "----------\n" << "Output\n";
for(int k=0; k<Size; k++) {
for(int l=0; l<Size; l++)
cout<<ArrayName[k*Size+l]<<" ";
cout << "\n";
}
}