AdventOfCode2024/Aufgabe 3/main.cpp

#include <iostream>
#include <vector>
#include <fstream>
#include <regex>

std::string readTextFromFile(const std::string& fileName) {
    std::vector<std::string> lines;
    std::ifstream file(fileName);
    if (!file) {  // Überprüft, ob die Datei geöffnet werden konnte
        std::cerr << "Fehler: Datei konnte nicht geöffnet werden: " << fileName << std::endl;
        return "";
    }
    std::string result;
    std::string s;
    while(getline(file, s)) {
       result += s;
    }
    return result;
}

int checkForSubstringBefore(std::string& content, const std::string substring, size_t startPosition) {
    size_t pos = 0;
    int previousOccurence = -1;
    while ((pos = content.find(substring, pos)) != std::string::npos) {
        if(pos > startPosition) {
            return previousOccurence;
        } else {
            previousOccurence = pos;
        }
        pos += substring.length();
    }
    return previousOccurence;
}

std::vector<std::string> determineValidMuls(std::string& content, bool checkEnabled=false) {
    std::vector<std::string> validMuls;

    std::regex regex(R"(mul\(\d{1,3},\d{1,3}\))");
    auto begin = std::sregex_iterator(content.begin(), content.end(), regex);
    auto end = std::sregex_iterator();

    for(auto it = begin; it != end; ++it) {
        if(checkEnabled) {
            int dont_start = checkForSubstringBefore(content, "don't()", it->position());
            int do_start = checkForSubstringBefore(content, "do()", it->position());

            if(dont_start < 0) {
                validMuls.push_back(it->str());
            } else if(do_start > dont_start) {
                validMuls.push_back(it->str());
            }
        } else {
            validMuls.push_back(it->str());
        }

    }
    return validMuls;
}


int calcMultOfMultOp(const std::string& multOp) {
    std::regex regex("\\d{1,3}");
    auto begin = std::sregex_iterator(multOp.begin(), multOp.end(), regex);
    auto end = std::sregex_iterator();

    int multResult = 1;
    for(auto it = begin; it != end; ++it) {
        multResult *= std::stoi(it->str());
    }
    return multResult;
}

int calcMultSum(std::vector<std::string>& validMuls) {
    int sum = 0;
    for(const auto& mul : validMuls) {
        sum += calcMultOfMultOp(mul);
    }
    return sum;
}

int main() {
    std::string content = readTextFromFile("../input.txt");
    std::vector<std::string> validMuls = determineValidMuls(content, false);

    int result = calcMultSum(validMuls);
    std::cout << "The correct Mult Result is: " << result << std::endl;

    std::vector<std::string> validMulsWithChecks = determineValidMuls(content, true);

    int resultWithChecks = calcMultSum(validMulsWithChecks);
    std::cout << "The correct Mult Result with check is: " << resultWithChecks << std::endl;
    return 0;
}