Issue with c++ referencing to function with 2d array

Question

I'm trying to get this matrix and print it out in the another function. The problem is that is impossible. I tried to solve it with ** and * but I got only the adress not the value but I cannot get the normal values as this in matrix 5x5. Can someone explain me what I do in a wrong way?

size_t matrix[5][5] =
    {
        {1, 16, 20, 23, 25},
        {6, 2, 17, 21, 24},
        {10, 7, 3, 18, 22},
        {13, 11, 8, 4, 19},
        {15, 14, 12, 9, 5},
    };
    set<bool> set1 = iterateover((size_t**)matrix)
     std::set<bool> iterateover(size_t** array)
    size_t numberofrows = sizeof(**arrayy) / sizeof(arrayy[0]);
    size_t numberofkols = sizeof(*arrayy[0]) / sizeof(arrayy[0][0]);
    std::set < bool >myset;
    for (size_t i = 0; i < numberofrows; i++)
    {
        for (size_t j = 0; j < numberofkols; j++)
        {
            std::cout << arrayy[i][j] << std::endl;
    return myset;

A double pointer is not the same as a 2d array. – Irelia Mar 12 '22 at 02:56 — Irelia, Mar 12 '22 at 02:56

score 1 · Answer 1 · answered Mar 12 '22 at 03:48

You can make iteratreOver a function template which can take a 2D array by reference, as shown below.

#include <iostream>
template<typename T,std::size_t N, std::size_t M>
void iterateOver(T (&arr)[N][M])
{
    for(std::size_t i= 0; i < N; ++i)
    {
        for(std::size_t j = 0; j < M; ++j)
        {
            std::cout<<arr[i][j] <<" ";
        }
        std::cout<<std::endl;
    }
}
int main()
{
    size_t matrix[5][5] =
    {
        {1, 16, 20, 23, 25},
        {6, 2, 17, 21, 24},
        {10, 7, 3, 18, 22},
        {13, 11, 8, 4, 19},
        {15, 14, 12, 9, 5},
    };
    //call iterateOver by passing the matrix by reference
    iterateOver(matrix);
   
}

The output of the above program can be seen here:

1 16 20 23 25 
6 2 17 21 24 
10 7 3 18 22 
13 11 8 4 19 
15 14 12 9 5

score 0 · Answer 2 · answered Mar 12 '22 at 03:13

you get row, col number incorrectly,it should be like this:

   size_t numberofrows =
        sizeof(matrix) / sizeof(matrix[0]);

    size_t numberofcols = sizeof(matrix[0]) / sizeof(matrix[0][0]);

and you want to print out to other function lets use template

template <typename T>
void print_matrix(T matrix, int numberofcols, int numberofrows)
{
    for (size_t i = 0; i < numberofrows; i++) {
        for (size_t j = 0; j < numberofcols; j++) {
            std::cout << matrix[i][j] <<" ";
        }
        std::cout << "\n";
    }
}

tested at : https://godbolt.org/z/vshev1e17

score 0 · Answer 3 · answered Mar 12 '22 at 03:29

0

if u want to define it in fun and print it in another function u need to do it dynamic not static or u can define it globally and access it from any function u defined check this Return a 2d array from a function

answered Mar 12 '22 at 03:29

mazen amr

90
6

Please do not use text speak ('u' vs 'you') and use correct punctuation (full stops at the end of sentences and capital letters at the beginning). If you are unsure, run it through an online spellchecker and formatter. – user438383 Mar 13 '22 at 13:04

Issue with c++ referencing to function with 2d array

3 Answers3