how to pass a 2D array to a function C++

[sarada purkait]

hiii
i want to pass a 2D array to a function .. the size of the array is not fixed .. i have tried using pointer to the array ..but it is giving error ..
what i wrote was :

       void fun(int *,int,int);
int main()
{
 
int ht,wd;
cin>>ht>>wd;
int arr[ht][wd];
int fun(&arr,ht,wd);
for(int k=0;k<ht;k++)
{
 
    for(int l=0;l<wd;l++)
    {
    cout<<arr[k][l];
    }
}
 
}
 
void fun(int*a,int h,int w)
{
for(int i=0;i<h;i++)
{
    for(int j=0;j<w;j++)
    {
        cout<<"roe"<<i<<"  ";
        cin>>*(a+i*w+j);
    }
}
}
 

can some1 help me wid dis .. i m fairly new to c++

[Extremist]

Please remember CODE tags

I'm not really seeing what you are asking, or what your code is doing
I would suggest that you get to know pointers first
You are asking how to pass a 2D array to a function C++
Wel, here is some code for that

First declare a 2D array

int ht=0, wd=0;
    cout << "Please enter the size of the array:  " << endl;
    cin >> ht;
    cin >> wd;
 
    int **array;               // Declaration, however, your declaration is also correct
 
    *array = new int[ht]; // Allocate some memory
    for(int i = 0; i < ht; i ++)
    {
        array[i] = new int[wd];
        for(int j = 0; j < wd; j ++)
        {
            array[i][j] = 0;
        }
 
    }
 

Passing that as an argument to a function would be :

void fun(int ** array, int ht, int wd)
{
    for(int i = 0; i < ht; i ++)
    {
        for(int j = 0; j < wd; j ++)
        {
            cout << array[i][j] << "\t";
        }
        cout << endl;
    }
}

calling that in the main function :

  fun(array, ht, wd);

[weaknessforcats]

This is not correct:

I'm not really seeing what you are asking, or what your code is doing
I would suggest that you get to know pointers first
You are asking how to pass a 2D array to a function C++
Wel, here is some code for that

First declare a 2D array

Code: ( text )
int ht=0, wd=0;
cout << "Please enter the size of the array: " << endl;
cin >> ht;
cin >> wd;

int **array; // Declaration, however, your declaration is also correct

*array = new int[ht]; // Allocate some memory
for(int i = 0; i < ht; i ++)
{
array[i] = new int[wd];
for(int j = 0; j < wd; j ++)
{
array[i][j] = 0;
}

}

Passing that as an argument to a function would be :

Code: ( text )
void fun(int ** array, int ht, int wd)
{
for(int i = 0; i < ht; i ++)
{
for(int j = 0; j < wd; j ++)
{
cout << array[i][j] << "\t";
}
cout << endl;
}
}

calling that in the main function :

Code: ( text )
fun(array, ht, wd);

An int** is a pointer-to-a-pointer-to-a-single-int. It is not a pointer to a 2D array.

For example, this array:

int arr[3][4];
 

has three elements. Each element is an array of 4 int. Now, the name of the array (arr) is the address of element 0. Therefore,the name of the array is trhe address of an array of 4 int. The address of an array of 4 int is declared as:

int (*ptr)[4];
 

That is what you use in your function calls. You will need a second argument for the number of these arrays in the array used on the call:

void MyFunction(int (*ptr)[4], int num)
{
 
}
 
int main()
{
    {
        int arr[3][4];
        MyFunction(arr, 3);
 
    }
}
 

If your array is allocated on the heap using the new operator, the address returned will be the address of an array of 4 int:

int (*arr)[4]   = new int[3][4];
 

[emaghero]

To pass a 2D array to a function proceed as follows

1. Declare memory for the array

int row,column;//Declare variables to hold the size of your array
 
cout<<"Input the size of your array\n";
cout<<"\n";
cout<<"Input the number of rows\n";
cin>>row;
cout<<"Input the number of columns\n";
cin>>column;
 
double *arr=new(double [row*column]);
//This declares memory for a dynamically allocated array of doubles
 
//It is always a good idea to initialise the array to zero before you use it
for(int i=0;i<row;i++){
    for(int j=0;j<column;j++){
         *(arr+i*column+j)=0.0;
    }
}
 
 

2. Define the function to which the array is to be passed

void function(double *array,int number_of_rows, int number_of_columns)
{
         //This function will print the array to the screen
          for(int i=0;i<number_of_rows;i++){
              for(int j=0;j<number_of_columns;j++)
                   cout<<*(array+i*number_of_columns+j)<<" ";
                   cout<<"\n";
          }
}
 

3. Pass the array to the function by calling it

//Perform some operation on the array here
 
//Call the function which passes the array
function(arr,row,column);
 
 

[weaknessforcats]

To pass a 2D array to a function proceed as follows

1. Declare memory for the array


Code: ( text )
int row,column;//Declare variables to hold the size of your array

cout<<"Input the size of your array\n";
cout<<"\n";
cout<<"Input the number of rows\n";
cin>>row;
cout<<"Input the number of columns\n";
cin>>column;

double *arr=new(double [row*column]); //This declares memory for a dynamically allocated array of doubles

//It is always a good idea to initialise the array to zero before you use it
for(int i=0;i<row;i++){
for(int j=0;j<column;j++){
*(arr+i*column+j)=0.0;
}
}

This is not allocating a 2D array. It is allocating a one-dimensional array.

Read my previous post.

[sarada purkait]

To pass a 2D array to a function proceed as follows

1. Declare memory for the array

int row,column;//Declare variables to hold the size of your array
 
cout<<"Input the size of your array\n";
cout<<"\n";
cout<<"Input the number of rows\n";
cin>>row;
cout<<"Input the number of columns\n";
cin>>column;
 
double *arr=new(double [row*column]);
//This declares memory for a dynamically allocated array of doubles
 
//It is always a good idea to initialise the array to zero before you use it
for(int i=0;i<row;i++){
    for(int j=0;j<column;j++){
         *(arr+i*column+j)=0.0;
    }
}
 
 

2. Define the function to which the array is to be passed

void function(double *array,int number_of_rows, int number_of_columns)
{
         //This function will print the array to the screen
          for(int i=0;i<number_of_rows;i++){
              for(int j=0;j<number_of_columns;j++)
                   cout<<*(array+i*number_of_columns+j)<<" ";
                   cout<<"\n";
          }
}
 

3. Pass the array to the function by calling it

//Perform some operation on the array here
 
//Call the function which passes the array
function(arr,row,column);
 
 

thankyou .. i can do it nw