Reverse string using recursion without specific seperators - c++

Question

I have an assignment which requires "Recursively reads one character at a time from the text file until a separator is encountered" -
Those non-separator characters are then displayed in reverse order, with the last character displayed being capitalized
Let's say file has below line and separator is !, white space and so on.
abc! ndtv
Expected output is:
Cba! Vtdn
I have written below code and I am getting the expected output — but one condition is I am supposed to do it using only two variables, and I am not able to do it with less than 3. Any pointers how to achieve it with 2 variables only?
int Reverse(ifstream &inFile, int level)
{
int myInput;
static int returnValue;
static int levelofinterest;
myInput = inFile.get();
if (!(isspace(myInput) || ((char)myInput == '.') ||
((char)myInput == '!') || ((char)myInput == ',') ||
((char)myInput == '?') || ((char)myInput == ';') ||
((char)myInput == ':') || ((char)myInput == '\0')||
myInput == EOF))
{
level++;
Reverse(inFile,level);
}
else
{
levelofinterest = level;
returnValue = myInput;
}
if(!(isspace(myInput) || ((char)myInput == '.') ||
((char)myInput == '!') || ((char)myInput == ',') ||
((char)myInput == '?') || ((char)myInput == ';') ||
((char)myInput == ':') || ((char)myInput == '\0')||
myInput == EOF))
{
level--;
if ((levelofinterest - 1) == level)
{
cout << (char)toupper(myInput);
}
else
{
cout.put((char)myInput);
}
}
return returnValue;
}

Answer 1

This code almost meets your requirements (but I'm not completely happy with it). It has only one extra variable over and above the arguments to the function. However, I altered the function signature — the code doesn't use the return value, so the function is defined as returning void. It probably can be modified to meet your alternative calling convention and the loop structure outlined in your (transcribed) comments.
#include <iostream>
#include <cctype>
using namespace std;
static void Reverse(istream &inFile, int level)
{
int c = inFile.get();
if (c == EOF)
return;
if (isalpha(c))
{
Reverse(inFile, level + 1);
if (level == 0)
cout << (char)toupper(c);
else
cout << (char)c;
}
else if (level > 0)
inFile.unget();
else
cout << (char)c;
}
int main()
{
while (cin)
Reverse(cin, 0);
return 0;
}
I call the source code recrevstr.cpp and compiled the program (using make) with the command:
g++ -O3 -g -std=c++11 -Wall -Wextra -Werror recrevstr.cpp -o recrevstr
and then run it:
$ ./recrevstr <<< 'abc! ndtv'
cbA! vtdN
$
It takes various short cuts. In particular, all non-alphabetic characters are delimiters. It uses an istream rather than an ifstream, and the main() is configured so standard input (aka cin) is processed. Like your sample code, it relies on a loop in the calling code to make sure the job is complete. I start with level 0; it's trivial to start with level 1 instead.
Note that any code using cout with << operators to produce output is inherently C++ and not directly applicable to C. This effect can be neutralized by using <cstdio> and FILE * (and stdin), plus appropriate I/O functions, which could then make it bilingual, though there'd need to be conditional compilation to get the std namespace out of the way.