int main()
{
  string s2("Hello C++!");
  cout << "最初的s2.size():" << s2.size() << endl;
  cout << "最初的s2.capacity():" << s2.capacity() << endl;
  s2.reserve(100);//扩容
  cout << "reserve(100)后的s2.size():" << s2.size() << endl;
  cout << "reserve(100)后的s2.capacity():" << s2.capacity() << endl;
  s2.shrink_to_fit();//缩容
  cout << "缩容后的s2.size():" << s2.size() << endl;
  cout << "缩容后的s2.capacity():" << s2.capacity() << endl;
  return 0;
}

int main()
{
  string s1("Hello C++!");//普通对象
  for (size_t i = 0; i < s1.size(); i++)
  {
    cout << s1[i];
  }
  cout << endl << "修改后:";
  for (size_t i = 0; i < s1.size(); i++)
  {
    cout << ++s1[i];//因为返回值是引用所以可以用[]对其进行修改
  }
  cout << endl;
  const string s2("Hello World!");
  for (size_t i = 0; i < s2.size(); i++)
  {
    cout << s2[i];
  }
  cout << endl;
  return 0;
}

int main()
{
  string s1("Hello C++!");//普通对象
  string::iterator it = s1.begin();
  while (it < s1.end())
  {
    cout << *it;//解引用迭代器
    it++;//++迭代器，让迭代器向后走
  }
  cout << endl;
  it = s1.begin();
  while (it < s1.end())
  {
    ++(*it);//通过迭代器去修改
    it++;
  }
  it = s1.begin();
  while (it < s1.end())
  {
    cout << *it;
    it++;
  }
  cout << endl;
  return 0;
}

int main()
{
  string s1("Hello C++!");//普通对象
  string::reverse_iterator it = s1.rbegin();
  while (it < s1.rend())
  {
    cout << *it;//解引用迭代器
    it++;//++迭代器，让迭代器向后走
  }
  cout << endl;
  return 0;
}

int main()
{
  string s1("Hello C++!");//普通对象
  for (auto it : s1)
  {
    cout << it;
  }
  cout << endl;
  for (auto& it : s1)//用引用就可以进行修改
  {
    it--;
  }
  for (auto it : s1)
  {
    cout << it;
  }
  cout << endl;
  return 0;
}

int main()
{
  string s1("Hello C++!");
  string s2("你好，C++！");
  cout << s2 << endl;//原始的s2
  s2 = s1;//string类对象
  cout << s2 << endl;//第一次赋值后的s2
  s2 = "春人.";
  cout << s2 << endl;//第二次赋值后的s2
  s2 = 'a';
  cout << s2 << endl;//第三次赋值后的s2
  return 0;
}

int main()
{
  string s1("Hello C++!");
  cout << "追加前：" << s1 << endl;
  s1.push_back('s');
  cout << "追加后：" << s1 << endl;
  return 0;
}

int main()
{
  string s1("Hello C++!");
  string s2("aaaa");
  cout << "追加前：" << s2 << endl;
  s2.append(s1);
  cout << "追加一个string对象：" << s2 << endl;
  s2 = "aaaa";
  s2.append(s1, 6, 3);
  cout << "追加一个string对象的一部分：" << s2 << endl;
  s2 = "aaaa";
  s2.append("你好");
  cout << "追加一个C类型的字符串：" << s2 << endl;
  s2 = "aaaa";
  s2.append("Hello!", 2);
  cout << "追加一个C类型字符串的前两个字符：" << s2 << endl;
  s2 = "aaaa";
  s2.append(5, 'b');
  cout << "追加五个字符b：" << s2 << endl;
  s2 = "aaaa";
  s2.append(s1.begin()+2, s1.begin()+4);
  cout << "追加一个迭代器区间：" << s2 << endl;
  return 0;
}

int main()
{
  string s1("Hello C++!");
  string s2("aaaa");
  cout << "追加前:" << s2 << endl;
  s2 += s1;
  cout << "追加一个string类对象:" << s2 << endl;
  s2 = "aaaa";
  s2 += "bcde";
  cout << "追加一个C类型的字符串:" << s2 << endl;
  s2 = "aaaa";
  s2 += 'o';
  cout << "追加一个字符:" << s2 << endl;
  return 0;
}

int main()
{
  string s2("Hello C++!");
  const char* str = s2.c_str();
  cout << str << endl;
  return 0;
}

int main()
{
  string s1("https://www.csdn.net/?spm=1011.2124.3001.4476");
  size_t pos1 = s1.find("csdn");
  cout << pos1 << endl;
  size_t pos2 = s1.find("www.csdn.net", 7, 3);
  cout << pos2 << endl;
  return 0;
}

int main()
{
    std::string str("The sixth sick sheik's sixth sheep's sick.");
    std::string key("sixth");
    std::size_t found = str.rfind(key);
    if (found != std::string::npos)
        str.replace(found, key.length(), "seventh");
    std::cout << str << '\n';
    return 0;
}

int main()
{
  string s1("https://www.csdn.net/?spm=1011.2124.3001.4476");
  size_t pos1 = s1.find("csdn");
  string s2 = s1.substr(pos1, 8);
  cout << s2 << endl;
  return 0;
}