How to properly delete multidemensional vector?

Question

So I am creating two different multidimensional vectors like this below

string **customdiceArray = new string*[crows];
for(unsigned int i = 0; i<crows;i++){
    customdiceArray[i] = new string[ccolumns];
}

They are giving me memory leaks however. I do a delete call like the one below for both vectors. Where am i going wrong?

//Deallocate create objects
delete diceArray;
diceArray = 0;

//set<string>* words = new set<string>;
delete words;
words = 0;

//string **customdiceArray = new string*[crows];
delete customdiceArray;
customdiceArray = 0;

You have to loop over the array deleting each element, then delete the array. — juanchopanza, Mar 12 '14 at 20:47
Like this: `std::vector> dice(crows, std::vector(ccolumns));` — Kerrek SB, Mar 12 '14 at 20:47
Good C++ programs contain almost no `delete` statements. If you actually used `vector` instead of arrays your code would be simpler and correct. — Alan Stokes, Mar 12 '14 at 20:54

score 1 · Accepted Answer · answered Mar 12 '14 at 20:51

1

So if you want use delete in proper way here some examples:

For one variable

string *i = new string;
delete i;

For arrays (one dimension)

string *i = new string[10];
delete[] i;

For arrays (multi dimensions)

string **i = new *string[10]
for(int j=0; j<10;++j){
   i[j] = new string[10];
}

for(int j=0; j<10;++j){
   delete[] i[j];
}
delete[] i;

answered Mar 12 '14 at 20:51

Ardel

315
2
9

Thank you very much Ardel. That solved my memory leak! – Elblonko Mar 12 '14 at 21:18

score 0 · Answer 2 · answered Mar 12 '14 at 21:36

To avoid memory leaks and write C++ native code, you can also use std::vector instead of C arrays which needs more caution and maintenance.

for example:

vector<vector<int> > matrix;

vector<int> cols;
cols.push_back(1);
cols.push_back(2);
cols.push_back(3);

matrix.push_back(cols);
matrix.push_back(cols);

for(int i=0; i<matrix.size(); i++)
  for(int j=0; j<cols.size(); j++)
    cout << matrix[i][j] << endl;

Result:

How to properly delete multidemensional vector?

2 Answers2