#include <stdio.h>
#include <string.h>

void revert(char* left, char* right) {
    if(left == right) return;

    char *ll = left; char* rr = right;

    char tmp = right[0];
    right[0] = left[0];
    left[0] = tmp;
    revert(++ll,--rr);
}

int main() {
    char rev_string[] = "Some teststring";
    printf("%sn", rev_string);
    revert(&rev_string[0],&rev_string[strlen(rev_string)-1]);//rev_string[strlen(rev_string)-1]);
    printf("%sn", rev_string);
    return 0;
}