Program:

#include <bits/stdc++.h>
using namespace std;

void allPossibleSubset(int arr[], int n)
{
    int count = pow(2, n);
    // The outer for loop will run 2^n times to print all subset .
    // Here variable i will act as a binary counter
    for (int i = 0; i < count; i++) {
        // The inner for loop will run n times , 
        // As the maximum number of elements a set can have is n
        // This loop will generate a subset
        for (int j = 0; j < n; j++) {
            // This if condition will check if jth bit in 
            // binary representation of  i  is set or not
            // if the value of (i & (1 << j)) is not 0 , 
            // include arr[j] in the current subset
            // otherwise exclude arr[j]
            if ((i & (1 << j)) != 0)
                cout << arr[j] << " ";
        }
        cout << "\n";
    }
}

int main()
{
    int n;
    
    cout << "Enter size of the set\n";
    cin >> n;

    int arr[n];
    cout << "Enter Elements of the set\n";
    for (int i = 0; i < n; i++)
        cin >> arr[i];

    allPossibleSubset(arr, n);

    return 0;
}

Output

Enter size of the set
4
Enter Elements of the set
1 2 3 4

1
2
1 2
3
1 3
2 3
1 2 3
4
1 4
2 4
1 2 4
3 4
1 3 4
2 3 4
1 2 3 4