#include <algorithm>
#include <vector>
using namespace std;

template <typename It>
void my_reverse (It start, It finish) {
    while (start < finish) {
        --finish;
        swap (*start, *finish);
        ++start;
    }
}

int main () {
    vector <int> arr = {0, 1, 2, 3, 4, 5, 6};
    my_reverse (arr.begin (), arr.end ());
    return 0;
}