How to create function with input is 2D array in C++

Question

I have a 2D array that defined as

int P[5][10];
for (int i=0;i<N;i++)
{
    for(int j=0;j<L;j++)
    {
        if(random()>0.5)
            P[i][j]=1;
        else
            P[i][j]=0;
    }
}

I want to make a function with input is P. The function allows us show the value of P. How to defined that function. I tried such as

void show_P(int P[][], int numcols,int numrows)

However, it is wrong. Could you help me fix it? Thanks

Answer 1

If you want to restrict the arguments to 5 by 10 2D arrays, you can pass by reference like this:

void show_P(int (&P)[5][10])

This will fail for any other type of array. If you want the function to work for other sizes, you can make it a template.

template <size_t N, size_t M>
void show_P(int (&P)[N][M])

Answer 2

You could just change it to:

void show_P(int** P, int numcols, int numrows) 

Passing 2D array always using the pointer.

Hope this will help.

Answer 3

Or using the std::array

void printArray(array<array<int,2>,3>& arr)
{
  for (auto x : arr)
  {
    for (auto y : x)
    {
      cout << y << endl;
    }
  }
}

int main()
{
  array<array<int,2>,3> arr{{{1, 2}, {2, 3}, {3, 4}}};
  arr[0][1] = 5;
  printArray(arr);
}

would give you:

1

5

2

3

3

4

Answer 4

void print( int (&ref)[5][10]) {

for( auto &lm: ref) // get the first array from the multidimensional array and initialize lm with it 
    for( auto &elem: lm) // get the first element from lm 
        std::cout << elem << " "; // print the element 

}

This only works with an array with dimensions as P ie, [5][10]

Answer 5

N=5;
L=10;    
void show_P( int ( &P )[N][L] )