aoc_2024_day1

#include <iostream>
#include <fstream>
#include <vector>
#include <sstream>
#include <algorithm>
#include <unordered_map>
#include <chrono>

std::pair<std::vector<int>, std::vector<int>> create_sorted_vectors_from_file(const std::string& file_name) {
    std::ifstream file(file_name);
    std::vector<int> col1, col2;
    std::string line;

    while (std::getline(file, line)) {
        std::istringstream iss(line);
        int num1, num2;
        if (iss >> num1 >> num2) {
            col1.push_back(num1);
            col2.push_back(num2);
        }
    }

    std::sort(col1.begin(), col1.end());
    std::sort(col2.begin(), col2.end());

    return {col1, col2};
}

int64_t calculate_l1_distance(const std::vector<int>& vec1, const std::vector<int>& vec2) {
    int64_t distance = 0;
    for (size_t i = 0; i < vec1.size(); ++i) {
        distance += std::abs(static_cast<int64_t>(vec1[i]) - vec2[i]);
    }
    return distance;
}

int64_t find_similarity_score(const std::vector<int>& vec1, const std::vector<int>& vec2) {
    std::unordered_map<int, unsigned int> vec2_counter;
    for (int el : vec2) {
        vec2_counter[el]++;
    }

    int64_t score = 0;
    for (int el : vec1) {
        auto it = vec2_counter.find(el);
        if (it != vec2_counter.end()) {
            score += static_cast<int64_t>(el) * it->second;
        }
    }
    return score;
}

int main() {
    auto start = std::chrono::high_resolution_clock::now();

    try {
        auto [col1, col2] = create_sorted_vectors_from_file(R"(C:\Users\msmin\code\aoc_python\day1_input.txt)");

        if (col1.size() == col2.size()) {
            int64_t l1_distance = calculate_l1_distance(col1, col2);
            int64_t similarity_score = find_similarity_score(col1, col2);
            std::cout << "L1 distance between the two vectors: " << l1_distance << std::endl;
            std::cout << "similarity score between the two vectors: " << similarity_score << std::endl;
        } else {
            std::cout << "Error: Vectors have different lengths" << std::endl;
        }
    } catch (const std::exception& e) {
        std::cout << "Error reading file: " << e.what() << std::endl;
    }

    auto end = std::chrono::high_resolution_clock::now();
    auto duration = std::chrono::duration_cast<std::chrono::microseconds>(end - start);
    std::cout << "Time elapsed: " << duration.count() << " microseconds" << std::endl;

    return 0;
}