Advent-of-Code/2022/2/main.cpp

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

enum RPS {
	Rock = 1,
	Paper,
	Scissors,
};

enum Result {
	Lose = 1,
	Draw,
	Win,
};

RPS ToRPS(char c)
{
	if(c == 'A' || c == 'X')
		return RPS::Rock;
	else if(c == 'B' || c == 'Y')
		return RPS::Paper;
	else if(c == 'C' || c == 'Z')
		return RPS::Scissors;

	std::cerr << "BAD DATA '" << c << "'." << std::endl;
	exit(-1);
}

int RPSScore(RPS rps)
{
	switch(rps)
	{
	case RPS::Rock:
		return 1;
	case RPS::Paper:
		return 2;
	case RPS::Scissors:
		return 3;
	}
}

bool Won(RPS us, RPS them)
{
	if(us == RPS::Rock && them == RPS::Scissors)
		return true;
	else if(us == RPS::Paper && them == RPS::Rock)
		return true;
	else if(us == RPS::Scissors && them == RPS::Paper)
		return true;

	return false;
}

RPS Which(RPS them, Result desired)
{
	if(desired == Result::Draw)
		return them; // same

	switch(them)
	{
	case RPS::Rock:
		if(desired == Result::Lose)
			return RPS::Scissors;
		return RPS::Paper;
	case RPS::Paper:
		if(desired == Result::Lose)
			return RPS::Rock;
		return RPS::Scissors;
	case RPS::Scissors:
		if(desired == Result::Lose)
			return RPS::Paper;
		return RPS::Rock;
	}
}

int Points(RPS us, RPS them)
{
	int rtn = 0;

	// score our play:
	rtn += RPSScore(us);

	// tie:
	if(us == them)
		return rtn + 3;
	// win:
	if(Won(us, them))
		return rtn + 6;
	// loss:
	return rtn;
}

int main()
{
	std::ifstream ifs("data.txt");
	if(!ifs.is_open())
	{
		std::cerr << "Missing data.txt." << std::endl;
		return -1;
	}

	unsigned long total = 0;
	unsigned long new_total = 0;

	for(std::string line; std::getline(ifs, line); )
	{
		char them = line[0];
		char us = line[2];

		Result r = Result::Lose;
		if(us == 'Y')
			r = Result::Draw;
		else if(us == 'Z')
			r = Result::Win;

		RPS todo = Which(ToRPS(them), r);

		total += Points(ToRPS(us), ToRPS(them));
		new_total += Points(todo, ToRPS(them));
	}

	std::cout << "    Total: " <<     total << std::endl;
	std::cout << "New Total: " << new_total << std::endl;

	return 0;
}