The correct way to initialize a dynamic pointer to a multidimensional array

From:https://stackoverflow.com/questions/18273370/the-correct-way-to-initialize-a-dynamic-pointer-to-a-multidimensional-array 

Let's start with some basic examples.

When you say int *P = new int[4];

1. new int[4]; calls operator new function()
2. allocates a memory for 4 integers.
3. returns a reference to this memory.

4. to bind this reference, you need to have same type of pointer as that of return reference so you do

   int *P = new int[4]; // As you created an array of integer
                        // you should assign it to a pointer-to-integer

For a multi-idimensional array, you need to allocate an array of pointers, then fill that array with pointers to arrays, like this:

int **p;
p = new int*[5]; // dynamic `array (size 5) of pointers to int`

for (int i = 0; i < 5; ++i) {
  p[i] = new int[10];
  // each i-th pointer is now pointing to dynamic array (size 10)
  // of actual int values
}

Here is what it looks like:

 

To free the memory

1. For one dimensional array,

    // need to use the delete[] operator because we used the new[] operator
   delete[] p; //free memory pointed by p;`

2. For 2d Array,

   // need to use the delete[] operator because we used the new[] operator
   for(int i = 0; i < 5; ++i){
       delete[] p[i];//deletes an inner array of integer;
   }
   
   delete[] p; //delete pointer holding array of pointers;

Avoid memory leakage and dangling pointers!