Passing a 2D array to a C++ function?

Question

I have a function which I want to take, as a parameter, a 2D array of variable size. So far I have this: void myFunction(double** myArray){ myArray[x][y] = 5; etc... } And I have declared an array elsewhere in my code: double anArray[10][10]; However, calling `myFunction(anArray)` gives me an error. I do not want to copy the array when I pass it in. Any changes made in `myFunction` should alter the state of `anArray`. If I understand correctly, I only want to pass in as an argument a pointer to a 2D array. The function needs to accept arrays of different sizes also. So for example, `[10][10]` and `[5][5]`. How can I do this?

Answer 1

using namespace std;

#include <iostream>

#include <stdlib.h>

int ** Matrix_Init( int nRows, int nCols)

{

int ** matrix = (int **) malloc( nRows * sizeof(int *));

if (matrix != NULL)

{

for (int iLoop=0; iLoop<nCols; iLoop++)

{

matrix[iLoop] = (int *) malloc(nCols*sizeof(int));

}

for (int iLoop=0; iLoop<nRows; iLoop++)

{

for (int jLoop=0; jLoop<nCols; jLoop++)

{

matrix[iLoop][jLoop]=0;

}

}

return(matrix);

}

}

void Matrix_Destroy(int ** matrix, int nRows)

{

for (int iLoop=0; iLoop<nRows; iLoop++)

{

if (matrix[iLoop]!=NULL)

{

free(matrix[iLoop]) ;

}

}

free(matrix);

}

void Matrix_Input ( int ** matrix, int nRows, int nCols)

{

for (int iLoop=0; iLoop<nRows; iLoop++)

{

for (int jLoop=0; jLoop<nCols; jLoop++)

{

cout << "Please input the value at row = " << (iLoop+1) << " : column " << (jLoop+1) << " :>";

cin >> matrix[iLoop][jLoop];

}

}

}

void Matrix_Dump( int ** matrix, int nRows, int nCols)

{

for (int iLoop=0; iLoop<nRows; iLoop++)

{

for (int jLoop=0; jLoop<nCols; jLoop++)

{

cout << matrix[iLoop][jLoop] << " ";

}

cout << endl;

}

}

int main()

{

int ** matrixA = Matrix_Init(5,5);

int ** matrixB = Matrix_Init(3,3);

Matrix_Input(matrixA, 5,5);

Matrix_Input(matrixB,3,3);

Matrix_Dump(matrixA,5,5);

Matrix_Dump(matrixB,3,3);

Matrix_Destroy(matrixA,5);

Matrix_Destroy(matrixB,3);

}