Question

This has been boggling me, the simple code:

int main()
{
    typedef std::string::size_type stype;
    std::cout << "What is your first name?\n";
    std::string first,second,fullname;
    std::cin >> first;
    std::cout << "What is your second name?\n";
    std::cin >> second;
    char * backwards;
    fullname = first + " " + second;
    stype fnsize = fullname.size();    
    backwards = new char [fnsize];
    stype b = 0;
    for(stype a = fnsize; a != 0; --a)
    {
       backwards[b++] = fullname[a - 1];
    }
    std::cout << backwards << std::endl;
    return 0;
}

Works most of the time, but when I write a name like my own, stanislaw terziev, I get an output veizret walsinatsslaw instead of veizret walsinats

Why is it so?

Answer 1

Two problems in your code.

First, you want backwards to be fnsize + 1 to allow for the end of string termination (required for a C-style string, not included in the std::string::size() method return value).

Second, make the last element of backwards a '\0' character (the end of string character). Without this, std::cout does not know where the char* ‘ends’ so you will sometimes get garbage characters. That is to say std::cout will keep outputting characters until it hits a '\0'.

A couple of other options you could look at as well:

1. Make backwards a std::string and use append(fullname[a-1])
2. Use std::reverse