Using pointer instead of array.

[Rampage]

Hi.Just started using pointers. I'm trying to use them instead of arrays but i get this error after the program finishes: Run-Time Check Failure #2 - Stack around the variable 'q' was corrupted. Anyway here's the code:

#include <iostream>
using namespace std;
int main ()
{int q=0,n,i,aux,j; int* p;
cout<<"Introduceti numarul de elemente:"; cin>>n;
p=&q;
for (i=1; i<=n; i++) cin>>*(p+i);
for (i=1; i<n; i++) for (j=i+1; j<=n; j++) if (*(p+i)>*(p+j)) {aux=*(p+i);
                                                               *(p+i)=*(p+j);
								*(p+j)=aux;}
for (i=1; i<=n; i++) cout<<*(p+i)<<" ";
return 0;
}

[firedraco]

q is only a single int, so you can't use it like it's an array. Anyway, arrays and pointers behave exactly the same way:

p[1] == *(p+1) regardless of whether or not p is an "array" or a "pointer".

[Rampage]

I'm trying to do this because with a pointer i can have an infinite number of spaces, also i use just as much memory as i need. With an array i got an error that its too long after trying to get more then 10¹⁰ spaces. Is there any way i can use a pointer this way?

[Skillless]

if you cant make an array that big, and cant allocate that amount with new

Then try an array of pointers if theres no other way

int** array = new int*[100000];
for(int i = 0; i < 100000; i++)
    array[i] = new int[100000];

then youll have a 2 dimensional array, containing a total of 10¹⁰ ints

But why would you even need 10¹⁰ ints?

pointers point to the start of an array by the way, theres not a big difference between a pointer to an array and an actual array

do know that this code will take up more or less than 40 GB of ram, so, good luck lol..

[harsh4u89]

@Rampage

You have first pointed the pointer p to the location of q

After that you are trying to access the memory locations adjacent to q

But those memory locations may not be a part of your program's memory location.

The program runs because there is no boundary check feature in c++.

for (i=1; i<=n; i++) cin>>*(p+i);


This code is illegally accessing the memory locations that are not part of your program.

[Rampage]

@Skillless
I needed that number of spaces for solving a problem at a contest. Anyway i didn't realized the size of memory it requires. So thx for pointing that out.

@harsh
is there any way i create a memory location each time i introduce a value? So that there always is a free memory location after the last introduced value?

[dserbia]

If you needed 10^10 array elements to solve it, your solution was probably wrong. There is certainly another solution.

If I understand your question, you want to create a dynamically resizing array. Vectors should do it. http://www.cplusplus.com/reference/stl/vector/

[Rampage]

Yes i realized that the solution was bad after i saw the required size. Thx for the link.