Write a C++ program to exchange the first and last characters in a given string and return the new string

#include <iostream>
using namespace std;

string test(string str)
        {
            return str.length() > 1
                ? str.substr(str.length() - 1) + str.substr(1, str.length() - 2) + str.substr(0, 1) : str;
        }
        
int main() 
 {
  cout << test("abcd") << endl;  
  cout << test("a") << endl;  
  cout << test("xy") << endl;  
  return 0;    
}