SKI Giveaway Solution

#include <algorithm>
#include <fstream>
#include <iostream>
#include <string>

std::string GetFileContent();
void ParseString(std::string & String);

void Starling(std::string & String);
void Kestrel(std::string & String);
std::string GetArgument(std::string & String);

int main()
{
    std::string String = GetFileContent();

    ParseString(String);
    std::cout << String << std::endl;

    system("pause");
}

std::string GetFileContent()
{
    std::ifstream Input("Input.txt");

    if (!Input.is_open())
    {
        std::cout << "Error opening Input File!" << std::endl;
        return "";
    }

    return std::string((std::istreambuf_iterator<char>(Input)), (std::istreambuf_iterator<char>()));
}

void ParseString(std::string & String)
{
    // Reverse String for efficiency
    std::string ReversedString(String.rbegin(), String.rend());
    String.assign("");

    size_t TermCharacterPosition;

    while ((TermCharacterPosition = ReversedString.find_last_of("$^!")) != std::string::npos)
    {
        char Term = ReversedString[TermCharacterPosition];
        String.append(ReversedString.rbegin(),
            std::reverse_iterator<std::string::iterator>(ReversedString.begin() + TermCharacterPosition) - 1);
        ReversedString.erase(TermCharacterPosition);

        switch (Term)
        {
        case '$': // Sxyz = xz (yz)
            Starling(ReversedString);
            break;
        case '^': // Kxy = x
            Kestrel(ReversedString);
            break;
        case '!': // Ix = x
            break;
        }

    }

    String.append(ReversedString.rbegin(), ReversedString.rend());

    String.erase(std::remove(String.begin(), String.end(), '('), String.end());
    String.erase(std::remove(String.begin(), String.end(), ')'), String.end());
}

void Starling(std::string & String)
{
    std::string Arg1 = GetArgument(String);
    std::string Arg2 = GetArgument(String);
    std::string Arg3 = GetArgument(String);

    String += ')' + Arg3 + Arg2 + '(' + Arg3 + Arg1;
}

void Kestrel(std::string & String)
{
    std::string Arg1 = GetArgument(String);
    std::string Arg2 = GetArgument(String);

    String += Arg1;
}

std::string GetArgument(std::string & String)
{
    if ((*String.rbegin()) == '(')
    {
        unsigned Count = 1;
        std::string::reverse_iterator Iter = String.rbegin() + 1;

        while (Count > 0)
        {
            switch (*Iter)
            {
            case '(': Count++;
                break;
            case ')': Count--;
                break;
            }

            ++Iter;
        }

        std::string Argument(Iter.base() + 1, String.end() - 1);
        String.erase(Iter.base(), String.end());
        return Argument;
    }
    else
    {
        std::string Argument(String.rbegin(), String.rbegin() + 1);
        String.erase(String.end() - 1);
        return Argument;
    }
}