How to swap function value and array element in for loop?

Question

How do I swap elements in the given code since I get message that expression must a modifiable lvalue? I need to swap function value and array element in a for loop.

int niz[2] = { 2,1 };
    int temp;
    for (int i = 0;i < 1;i++)
    {
        temp = niz[i];
        niz[i] = minimum(niz, 2, i);
        minimum(niz, 2, i) = temp;

    }
    for (int i = 0;i < 2;i++)
    {
        cout << niz[i] << endl;
    }

Answer 1

#include <iostream>

using namespace std;

void swap(int arr[], int size);

int main(void) {
    int x[2] = {2, 1};

    cout << "Before: ";

    for (int i = 0; i <= 1; i++) {
        cout << x[i] << ", ";
    }

    swap(x, 2);

    cout << endl << "After: ";

    for (int i = 0; i <= 1; i++) {
        cout << x[i] << ", ";
    }

    return 0;
}

void swap(int arr[], int size) {
    for (int i = 0; i < size / 2; i++) {
        arr[i] ^= arr[size - 1 - i];
        arr[size - 1 - i] ^= arr[i];
        arr[i] ^= arr[size - 1 - i];
    }
}

Hope it helps you.