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!