#include #include #include "mystring.h" main() { string str1, str2; const char *s2; char *s3; str1 = "Hello World"; printf("%d %s\n", str1.length(), str1.c_str()); cout << str1.length() << " " << str1 << "\n"; str2 = str1; cout << str2 << "\n"; str1[0] = 'J'; cout << str1 << "\n" << str2 << "\n"; s2 = str2.c_str(); cout <