Adding/Removing Elements in an Array Inside a Function Using Pointers - c++

Question

I am trying to figure this problem out. This is for a project and our instructor requires this header. I got the check function working properly but adding when adding to the array we must use a pointer. My understanding is that we should copy this array to another array and replace the pointer. For example Array1 {1,2,3} then copy it to Array2 {1,2,3,4} then add 4 to expand the array. Unfortunately everything I have found researching.. vectors and other functions would be better suited for this task but we are required to only use the pointer and the size to resize and add the element.
// returns the index of the element in "arrayPtr" of "size"
// that corresponds to the element holding "number"
// if number is not in the array, returns -1
int check(int *arrayPtr, int number, int size);
// adds "number" to the array pointed to by "arrayPtr" of "size".
// if the number is not already there, if "number" is there - no action
// Note, the size of the array is thus increased.
void addNumber(int *& arrayPtr, int number, int &size);
// removes a "number" from the "arrayPtr" of "size".
// if "number" is not there -- no action
// note, "size" changes
void removeNumber(int *& arrayPtr, int number, int &size);
I have this so far:
// returns the index of the element in "arrayPtr" of "size"
// that corresponds to the element holding "number"
// if number is not in the array, returns -1
int check(int *arrayPtr, int number, int size) {
for (int i = 0; i < size; i++) {
if (arrayPtr[i] == number) {
return i;
}
}
return -1;
}
// adds "number" to the array pointed to by "arrayPtr" of "size".
// if the number is not already there, if "number" is there - no action
// Note, the size of the array is thus increased.
void addNumber(int *& arrayPtr, int number, int &size) {
if (check(arrayPtr, number, size)==-1) {
//add the element to the end of the array
}
//did not run if -1
}
// removes a "number" from the "arrayPtr" of "size".
// if "number" is not there -- no action
// note, "size" changes
void removeNumber(int *& arrayPtr, int number, int &size) {
}
Any hints or tips or suggestions on how to proceed would be appreciated!

Answer 1

To be more clear what you are trying to build is an Set like data structure (because you are avoiding duplicates).
Another thing from you code is you have big chunck of memory allocated for this purpose and you are just access it with the arrayPtr and size.
If this is the case You might be maintaining a MAX_MEMORY_SIZE.
something like
#define MAX_MEMORY_SIZE 1000000
Have this assumption,
Algorithm for addNumber:
If size+1 >= MAX_MEMORY_SIZE return an 'overflow or max memory' exception
Check for existence of new element
If found, do nothing and simply return
If not found, copy the new element # arrayPtr[size] (arrayPtr[size] = number). (You may choose to keep them in some order so that your search can be effective as well. For that your check function and implementation has to be different)
Increase the size
Algorithm for removeNumber:
Check for existence of given element
If not found, do nothing and simply return
If found, loop the all the elements array and shift 1 position left. A code like below.
Decrease the size
Hope this will take you to next level.
position = check(arrayPtr, number, size);
for (i = position; i < size-1; i++) {
arrayPtr[i] = arrayPtr[i+1];
}