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];

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

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

For one dimensional array,

 // need to use the delete[] operator because we used the new[] operator

delete[] p; //free memory pointed by p;`

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!

巴特西

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

To free the memory

最新文章

热门文章