c++ 中的字符串到字符数组

Question

I was making a simple program in c++ to convert a string to a char array and then print it out. My code is:

string UserImput;
int lenght;

 
 void Test()
{
     getline(cin, UserImput);
     
     lenght = UserImput.size();

     char char_array[lenght + 1];
     copy(UserImput.begin(), UserImput.end(), char_array);

    
     cout << char_array;
   
}

The error I am getting is "expression must have a costant value" and I do not know why.

Answer 1

In char char_array[lenght + 1]; , lenght + 1 is not a compile-time constant. The size of an array must be known at compile-time. Since the value of length is not known until runtime, you will need to allocate memory dynamically in this situation. For example:

char* char_array = new char[lenght + 1];

Don't forget to delete the array when you are done:

delete[] char_array;

Answer 2

You can use:

  char* c = _strdup(UserImput.c_str());

But I wonder - why? Just to output it to cout ? Then you can do:

cout << UserImput.c_str();