reverse

#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
using namespace std;
void my_reverse(string& s, int c = 0) {
  if (!c) c = (int) s.size() - 1;
  for (int i = 0, j = c; i < j; i++, j--) {
    char t = s[i];
    s[i] = s[j];
    s[j] = t;
  }
}
int main() {
  string s1 = "This is a test.";
  string s2 = "I like C++.";
  string s3 = s1;
  string s4 = s2;
  my_reverse(s1);
  my_reverse(s2, 7);
  reverse(s3.begin(), s3.end());
  reverse(s4.begin(), s4.begin() + 7 + 1);
  cout << s1 << endl;
  cout << s2 << endl;
  cout << s3 << endl;
  cout << s4 << endl;
}