aoc25/day8/main.cpp

#include <algorithm>
#include <cmath>
#include <cstddef>
#include <expected>
#include <format>
#include <fstream>
#include <functional>
#include <iostream>
#include <map>
#include <print>
#include <ranges>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>

using Point = std::tuple<int, int, int>;

static auto getDistance(const Point &a, const Point &b) -> double {
    return sqrt(pow(std::get<0>(a) - std::get<0>(b), 2) + pow(std::get<1>(a) - std::get<1>(b), 2) +
                pow(std::get<2>(a) - std::get<2>(b), 2));
}

static auto parseInput(const std::string &filename) -> std::expected<std::vector<Point>, std::string> {
    std::ifstream inputF{filename};

    if (!inputF) {
        return std::unexpected{"Some file open error."};
    }

    std::vector<Point> pointVec{};

    std::string puzzleLine;
    while (std::getline(inputF, puzzleLine)) {
        if (!puzzleLine.empty()) {
            auto subParts = std::ranges::to<std::vector<std::string>>(std::views::split(puzzleLine, ','));
            pointVec.emplace_back(std::stoi(subParts[0]), std::stoi(subParts[1]), std::stoi(subParts[2]));
        }
    }
    // std::println("pointList: {}", pointVec);
    return pointVec;
}

static auto getCombinations(const std::vector<Point> &pointVec) -> std::vector<std::pair<Point, Point>> {
    std::vector<std::pair<Point, Point>> result;

    result.reserve(pointVec.size() * pointVec.size());

    for (size_t i = 0; i < pointVec.size(); ++i) {
        for (size_t j = i + 1; j < pointVec.size(); ++j) {
            result.emplace_back(pointVec[i], pointVec[j]);
        }
    }
    return std::move(result);
}

static auto getDistances(const std::vector<Point> &pointVec) -> auto {
    auto comparisonLamb = [](const std::pair<Point, Point> &pair1, const std::pair<Point, Point> &pair2) -> bool {
        return getDistance(pair1.first, pair1.second) < getDistance(pair2.first, pair2.second);
    };
    std::map<std::pair<Point, Point>, double, decltype(comparisonLamb)> sortedMap(comparisonLamb);

    auto combinations = getCombinations(pointVec);
    for (const auto &combination : combinations) {

        // std::println("Combinations: {}:{}", combination.first, combination.second);
        sortedMap[combination] = getDistance(combination.first, combination.second);
    }

    return sortedMap;
}

static auto doTheThing(const std::vector<Point> &pointVec, int numberToTake) -> long long {
    auto distanceMap = getDistances(pointVec);
    std::map<Point, int> pointToCircuitMap{};
    std::unordered_map<int, std::vector<Point>> circuitMap;
    int currentCircuit = 0;
    for (const auto &[combination, distance] : distanceMap) {
        const auto &[left, right] = combination;
        // std::println("DistanceMap: {}:{} = {}", left, right, distance);

        if (pointToCircuitMap.contains(left) && pointToCircuitMap.contains(right)) {
            int leftCircuit = pointToCircuitMap[left];
            int rightCircuit = pointToCircuitMap[right];
            // std::println("Left circuit: {}. Right circuit: {}", leftCircuit, rightCircuit);
            if (leftCircuit != rightCircuit) {
                std::println("Merge: {} to {}", left, right);

                for (const auto &rightCircuitPoint : circuitMap[rightCircuit]) {
                    pointToCircuitMap[rightCircuitPoint] = leftCircuit;
                }
                circuitMap[leftCircuit].append_range(circuitMap[rightCircuit]);
                circuitMap.erase(rightCircuit);

                // std::println("mergesize: {}", circuitMap[leftCircuit].size());
                if (circuitMap[leftCircuit].size() >= pointVec.size()) {

                    return (long long)std::get<0>(left) * (long long)std::get<0>(right);
                }
            }
        } else if (pointToCircuitMap.contains(left)) {
            int leftCircuit = pointToCircuitMap[left];
            // std::println("Only left exists: {} to {}", left, right);
            pointToCircuitMap[right] = pointToCircuitMap[left];

            circuitMap[leftCircuit].push_back(right);
            // std::println("leftsize: {}", circuitMap[leftCircuit].size());
            if (circuitMap[leftCircuit].size() >= pointVec.size()) {

                return (long long)std::get<0>(left) * (long long)std::get<0>(right);
            }
        } else if (pointToCircuitMap.contains(right)) {
            int rightCircuit = pointToCircuitMap[right];
            // std::println("Only right exists: {} to {}", left, right);
            pointToCircuitMap[left] = pointToCircuitMap[right];

            circuitMap[rightCircuit].push_back(left);
            // std::println("rightsize: {}", circuitMap[rightCircuit].size());
            if (circuitMap[rightCircuit].size() >= pointVec.size()) {

                return (long long)std::get<0>(left) * (long long)std::get<0>(right);
            }
        } else {
            currentCircuit++;
            pointToCircuitMap[left] = currentCircuit;
            pointToCircuitMap[right] = currentCircuit;

            circuitMap[currentCircuit].push_back(left);
            circuitMap[currentCircuit].push_back(right);
        }
    }
    // std::println("pointToCircuitMap: {}", pointToCircuitMap);

    std::println("circuitMap");
    for (const auto &[circuit, pointsInCircuit] : circuitMap) {

        std::println("{} : {}", circuit, pointsInCircuit);
    }

    auto sizesOfLists = circuitMap | std::views::transform([](const auto &kvp) -> int { return kvp.second.size(); }) |
                        std::ranges::to<std::vector<int>>();
    std::ranges::sort(sizesOfLists, std::greater{});
    auto threeLargest = std::ranges::fold_left(sizesOfLists | std::views::take(3), 1, std::multiplies{});

    // std::println("{}", threeLargest);
    return threeLargest;
}

auto main() -> int {
    auto testCase = parseInput("test_input");
    if (testCase) {
        constexpr int TEST_PUZZLE_TAKE = 10;

        auto testResult = doTheThing(*testCase, TEST_PUZZLE_TAKE);
        std::println("P1 Testcase result: {}", testResult);

        // auto testResultP2 = treePartTwo(*testCase);
        // std::println("P2 Testcase result: {}", testResultP2);
    } else {
        std::print("{}\n", testCase.error());
    }

    auto realPuzzle = parseInput("puzzle_input");
    if (realPuzzle) {
        constexpr int REAL_PUZZLE_TAKE = 1000;
        // auto realResult = doTheThing(*realPuzzle, REAL_PUZZLE_TAKE);
        // std::println("P1 Real result: {}", realResult);

        auto realResultP2 = doTheThing(*realPuzzle, REAL_PUZZLE_TAKE);
        std::println("P2 Real result: {}", realResultP2);
    } else {
        std::print("{}\n", realPuzzle.error());
    }

    return 0;
}