#include <cstdlib>
#include <cstring>
#include <iostream>

using namespace std;

void reverse(char* str)
{
    size_t n = strlen(str);
    size_t n_half = n/2;
    for (size_t i = 0; i < n_half; ++i)
    {
        size_t ri = n - i - 1;
        swap(str[i], str[ri]);
    }
}

int main(int argc, char** argv)
{
    if (argc < 2)
    {
        cout << "needs at least one argument" << endl;
        return EXIT_FAILURE;
    }

    char* p = argv[1];
    cout << "input string: " << p << endl;
    reverse(p);
    cout << "reversed: " << p << endl;

    return EXIT_SUCCESS;
}