C++ STL string字符存取

#include
#include
using namespace std;
void test01(){
string str="hello";
//1.通过[]访问单个字符 
for(int i=0;i<str.size();i++){
	cout<<str[i]<<" ";
} 
cout<<endl;

//2.通过at方式访问单个字符
for(int j=0;j<str.size();j++){
	cout<<str.at(j)<<" ";
}  cout<<endl;
//也可以修改单个字符 
str[0]='x';
cout<<str<<endl;
str.at(1)='x';
cout<<str<<endl; }

int main()
{ 
  test01();
  return 0; 
}