Thread: problem with getline() file I/O

[sorry the title is misleading/incorrect. I edited my post, but couldnt change the title]
Hi all, I'm having a problem with a function that is supposed to reverse a string. When i Run it, I'm getting a box that says

the instruction at "some hex address" referenced memory at "some other hex address." The memory could not be "written"

Thanks for any help you can give me

Here is my code

Code:

string szReverse(string szString)
{
	string szNewString;
	int iLength = szString.length();
	for (int i = 0; i < iLength; i++)
	{
		szNewString[i] = szString[iLength - i - 1];
	}
	
	return szNewString;
}

>Use a second string store your reversed string.
He did already. I think it's probably because when you instantiate "szNewString", it's empty (it's length() = 0). Try, first, to set its length equal to "szString", and then copy it.

Standard containers such as vector and string are not like their builtin equivalents (arrays if you were wondering). You can declare and use a container before it has any elements, they grow dynamically. You cannot use the subscript operator of a standard container if the element does not already exist. In your case, you can either resize szNewString manually:

Code:

string szReverse(string szString)
{
  string szNewString;
  int iLength = szString.length();

  szNewString.resize(iLength);
  for (int i = 0; i < iLength; i++)
  {
    szNewString[i] = szString[iLength - i - 1];
  }

  return szNewString;
}

Or build it dynamically instead of treating it as you would an array:

Code:

string szReverse(string szString)
{
  string szNewString;
  int iLength = szString.length();

  for (int i = 0; i < iLength; i++)
  {
    szNewString += szString[iLength - i - 1];
    // or
    // szNewString.push_back ( szString[iLength - i - 1] );
  }

  return szNewString;
}

See also Uses and Abuses of Vector for a similar discussion.