#include <iostream>
#include <fstream>
#include <vector>
#include <optional>


int calcNumOfEncounteredTrees(
        const std::vector<std::vector<bool>>& world,
        const std::pair<int, int> dimensions,
        std::pair<int, int> slope
    ) {
        int treeCount = 0;
        int x = 0;

        for (int y = 0; y < dimensions.second; y += slope.second) {
            if (!world[y][ x % dimensions.first]) treeCount++;
            x += slope.first;
        }

        return treeCount;
}



void part1(const std::vector<std::vector<bool>>& world, const int width, const int height) {
    const int RISE = 1;
    const int RUN = 3;

    int count = calcNumOfEncounteredTrees(world, { width, height }, { RISE, RUN });
    std::cout << "(P1) Number of trees: " << count << std::endl;
}

void part2(const std::vector<std::vector<bool>>& world, const int width, const int height) {
    int count1 = calcNumOfEncounteredTrees(world, { width, height }, { 1, 1 });
    int count2 = calcNumOfEncounteredTrees(world, { width, height }, { 3, 1 });
    int count3 = calcNumOfEncounteredTrees(world, { width, height }, { 5, 1 });
    int count4 = calcNumOfEncounteredTrees(world, { width, height }, { 7, 1 });
    int count5 = calcNumOfEncounteredTrees(world, { width, height }, { 1, 2 });

    uint64_t product = count1 * count2 * count3 * count4 * count5;
    std::cout << "(P2) Product of number of trees: " << product << std::endl;
}


int main() {
    std::ifstream input { "../input.txt" };
    std::vector<std::vector<bool>> world;
    std::optional<int> maybeWidth = std::nullopt;
    int lineCount = 0;

    std::string line;
    while(std::getline(input, line)) {
        if (!maybeWidth.has_value()) maybeWidth = { line.length() };

        std::vector<bool> row;
        for (char c : line) row.push_back(c == '.');
        world.push_back(row);

        lineCount++;
    }

    part1(world, maybeWidth.value(), lineCount);
    part2(world, maybeWidth.value(), lineCount);
}