Allocate memory 2d array in function C++

Question

I'm trying to dynamically allocate memory for a 2D array inside a function in C++. A question exactly like this has been asked except that it is written using malloc and dealloc, so I was wondering if you could help me convert it to use new and delete. Here is the other question:

Allocate memory 2d array in function C

I tried changing it to the following code, but I'm getting errors.

void assign_memory_for_board(int ROWS, int COLS, int *** board) {
   *board = new int**[ROWS];
   for (int i = 0; i < ROWS; i++) {
       (*board)[i] = new int*[COLS];
   }
}

Here is the answer that worked using malloc and dealloc:

void allocate_mem(int*** arr, int n, int m)
{
   *arr = (int**)malloc(n*sizeof(int*));
   for(int i=0; i<n; i++)
      (*arr)[i] = (int*)malloc(m*sizeof(int));
}

Thank you!

Why so many stars? Just use appropriate standard containers. — πάντα ῥεῖ, Mar 08 '16 at 02:10
Unless otherwise constrained, always prefer `std::vector` or `std::array`, and consider using a 2D view to a 1D physical array. — , Mar 08 '16 at 02:11
Hello everyone, why was this question downvoted 3 times? I'd like to know so I can ask better questions later. — IgnisImperatrix, Mar 12 '16 at 00:23

score 0 · Accepted Answer · answered Mar 08 '16 at 02:19

0

You have extra stars. The function should be

void assign_memory_for_board(int ROWS, int COLS, int *** board) {
   *board = new int*[ROWS];
   for (int i = 0; i < ROWS; i++) {
       (*board)[i] = new int[COLS];
   }
}

answered Mar 08 '16 at 02:19

MikeCAT

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Thank you very much! So does C++ take care of some of the pointers? Because in C there were more pointers. – IgnisImperatrix Mar 08 '16 at 02:23
They say [you shouldn't cast the result of `malloc()` in C](http://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc). – MikeCAT Mar 08 '16 at 02:23
`char* hoge = new char[10];` <- ` = new [];` – MikeCAT Mar 08 '16 at 02:26

score 0 · Answer 2 · answered Apr 02 '19 at 09:19

0

try it

int AllocMatrix(int ***K, int h, int c){
    *K = new int *[h];
    for(int i=0; i < h; i++){
        *K[i] = new int[c];
    }
    if(K == NULL){
        return 0;
    }
    cout<<"Avaiable!"<<endl;
    return 1;
}

answered Apr 02 '19 at 09:19

Ngọc Anh Hoàng

1
1

Allocate memory 2d array in function C++

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