Question

Currently I’m writing a rather extensive homework assignment that – among other things – reads a file, builds a binary search tree and outputs it.

Somewhere inside all that I’ve written a recursive method to output the values of the binary search tree in order.

void output(node* n)
{
if(n->leftChild != NULL)
    output(n->leftChild);
cout << n->keyAndValue << " || ";
outputString += n->keyAndValue << '|';
if(n->rightChild != NULL)
    output(n->rightChild);
}

No problem with that, but you’ll notice the line outputString += n->keyAndValue << '|';, because I also want to have all the values inside a char array (I am not allowed to use strings or other more current features of C++) that I can use later on in a different method (e.g. Main method).

The Char-Array is declared as follows:

char *outputString;

This being just one of the ways I’ve tried. I also tried using the const keyword and just regularly building an array char outputString[]. With the version I’ve shown you I encounter an error when – later on in the program in a different method – calling the following code:

cout << outputString;

I get the following error:

Unhandled exception at 0x008c2c2a in BST.exe: 0xC00000005: Access Violation reading location 0x5000000000.

Any clue as to how I’d be able to build a dynamic char array, assign values to it numerous times using += and outputting it without triggering an access violation? I am sorry for asking a rather basic question but I am entirely new to C++.

Thanks and Regards,

Dennis

Answer 1

+= on pointers does pointer arithmetic, not string concatenation. Eventually you get way beyond your array that outputString was pointing to, and trying to print it leads to a segfault.

Since you can’t use std::string, you need to use strcat along with new[] and delete[] and make sure you allocated your original array with new[].