Segmentation fault when remove duplicate value in pointer array - c++

Question

When debugging, I found that segmentation fault caused after copy from temp array (b) to original array (a), I don't know how to solve this, can you guys help me on that?
#include <iostream>
using namespace std;
int main() {
int n;
cout << "n = ";
cin >> n;
int *a = new int[n];
for (int i = 0; i < n; i++)
cin >> a[i];
cout << "\nNumber to remove: ";
int k;
cin >> k;
for (int i = 0; i < n; i++)
{
while (a[i] == k && i < n - 1)
{
int *b = new int[n]{0};
for (int j = 0; j < i; j++)
b[j] = a[j];
for (int j = i + 1; j < n; j++)
b[j - 1] = a[j];
a = NULL;
delete a;
n--;
int *a = new int[n];
for (int j = 0; j < n; j++)
a[j] = b[j];
}
}
cout << "Result: ";
for (int i = 0; i < n; i++)
cout << a[i] << " ";
}

Answer 1

The problem with this implementation lies here:
a = NULL;
delete a;
When you use the delete keyword you are telling the compiler to free the memory allocated by a new keyword, in this case you have a which is a pointer to the memory allocated by int *a = new int[n];. a at this point would probably be a 32bit address for example 0xbfebd5c0, i said probably because it depends on the architecture of the machine, however... after that you are setting a to NULL resulting in a being 0x0, at the next while condition check a is NULL and accessing 0x0 + i is not possible due to safety reasons imposed by the OS (no one gave you access to this location). The solution to your specific problem would be removing a = NULL; and delete a; as both these operations interfere with the while condition check.
I would suggest to take another approach at solving this problem since you really don't need to do this many dynamic allocations.