W3School TIY Editor

#include <iostream>

#include <string>

using namespace std;

​

int main() {

  string myString = "Hello";

  cout << "原始字符串: " << myString << "\n";

  cout << "第一个字符: " << myString.at(0) << "\n";

  cout << "第二个字符: " << myString.at(1) << "\n";

  cout << "最后一个字符: " << myString.at(myString.length() - 1) << "\n";

  myString.at(0) = 'J';

  cout << "修改后的字符串: " << myString;

  return 0;

}