Day 14

Author: bt

CMakeLists.txt

@@ -21,6 +21,8 @@ add_challenge(day9)
 add_challenge(day10)
 add_challenge(day11)
 add_challenge(day12)
+add_challenge(day13)
+add_challenge(day14)
 
 add_custom_command(TARGET day1
     COMMAND ${CMAKE_COMMAND} -E create_symlink "${CMAKE_CURRENT_SOURCE_DIR}/data" "./data"

include/Point.hpp include/Position.hppinclude/Point.hpp renamed to include/Position.hpp

@@ -0,0 +1,190 @@
+#include "common_headers.hpp"
+#include "Position.hpp"
+
+#include <cmath>
+#include <regex>
+
+struct RobotInfo final
+{
+    Position position{};
+
+    int velocityX{};
+    int velocityY{};
+};
+
+[[nodiscard]] size_t solveFirstPart(const std::vector<RobotInfo>& inputVec)
+{
+    constexpr size_t width{101};
+    constexpr size_t height{103};
+    constexpr size_t midVertical{(width / 2) + 1};
+    constexpr size_t midHorizontal{(height / 2) + 1};
+    std::array<int, 4> counters{};
+    std::vector<std::vector<int>> map(height, std::vector<int>(width));
+
+    for(const auto& robot : inputVec) {
+        int64_t newX{robot.position.x + robot.velocityX * 100};
+        int64_t newY{robot.position.y + robot.velocityY * 100};
+        if(newX < 0) {
+            newX = (width - (std::abs(newX) % width)) % width;
+        }
+        else {
+            newX = newX % width;
+        }
+        if(newY < 0) {
+            newY = (height - (std::abs(newY) % height)) % height;
+        }
+        else {
+            newY = newY % height;
+        }
+        if(newX != midVertical-1 && newY != midHorizontal-1) {
+            counters[2 * (newY / midHorizontal) + newX / midVertical]++;
+        }
+        map[newY][newX]++;
+    }
+
+    return std::accumulate(counters.begin(), counters.end(), size_t{1}, std::multiplies<>{});
+}
+
+[[nodiscard]] double EuclideanDistanceFromOrigin(double x, double y) noexcept
+{
+    return std::sqrt(x * x + y * y);
+}
+
+[[nodiscard]] double calculateVariance(const std::vector<std::vector<int>>& matrix) noexcept
+{
+    const size_t midVertical{(matrix[0].size() / 2) + 1};
+    const size_t midHorizontal{(matrix.size() / 2) + 1};
+
+    double positionCount{};
+    double meanDistance{};
+    for(size_t i = 0; i < matrix.size(); ++i) {
+        for(size_t j = 0; j < matrix[0].size(); ++j) {
+            positionCount += matrix[i][j] != 0;
+            meanDistance += matrix[i][j] * EuclideanDistanceFromOrigin(i, j);
+        }
+    }
+    meanDistance /= positionCount;
+
+    double variance{};
+    for(size_t i = 0; i < matrix.size(); ++i) {
+        for(size_t j = 0; j < matrix[0].size(); ++j) {
+            const auto d{EuclideanDistanceFromOrigin(i, j)};
+            variance += matrix[i][j] * (d - meanDistance) * (d - meanDistance);
+        }
+    }
+
+    return variance;
+}
+
+
+[[nodiscard]] size_t solveSecondPart(const std::vector<RobotInfo>& inputVec) {
+    constexpr size_t width{101};
+    constexpr size_t height{103};
+    std::vector<std::vector<int>> map(height, std::vector<int>(width));
+    
+    std::unordered_map<double, size_t> varianceFreq;
+    
+    double minVariance{std::numeric_limits<double>::max()};
+    size_t minVarianceId{};
+
+    size_t iteration{};
+    while(++iteration < 10000) {
+        map.clear();
+        map.resize(height, std::vector<int>(width));
+
+        for(const auto& robot : inputVec) {
+            int64_t newX{robot.position.x + robot.velocityX * iteration};
+            int64_t newY{robot.position.y + robot.velocityY * iteration};
+            if(newX < 0) {
+                newX = (width - (std::abs(newX) % width)) % width;
+            }
+            else {
+                newX = newX % width;
+            }
+            if(newY < 0) {
+                newY = (height - (std::abs(newY) % height)) % height;
+            }
+            else {
+                newY = newY % height;
+            }
+            map[newY][newX] = 1;
+        }
+        const double variance{calculateVariance(map)};
+        varianceFreq[variance]++;
+        if(variance < minVariance) {
+            minVariance = variance;
+            minVarianceId = iteration;
+        }
+    }
+
+    return minVarianceId;
+}
+
+
+[[nodiscard]] RobotInfo parseRobotInfo(const std::string& input) {
+    RobotInfo info;
+
+    // Define the regex pattern to match key-value pairs like "p=0,4" or "v=3,-3"
+    std::regex pattern(R"((\w+)=(-?\d+),(-?\d+))");
+    std::smatch matches;
+
+    // Use an iterator to find all matches in the input string
+    auto begin = std::sregex_iterator(input.begin(), input.end(), pattern);
+    auto end = std::sregex_iterator();
+
+    for (auto it = begin; it != end; ++it) {
+        matches = *it;
+
+        // Extract key and coordinates
+        const std::string key = matches[1];
+        const int x{std::stoi(matches[2])};
+        const int y{std::stoi(matches[3])};
+
+        // Store the parsed values in the map
+        if(key == "p") {
+            info.position = Position{x, y};
+        }
+        else if(key == "v") {
+            info.velocityX = x;
+            info.velocityY = y;
+        }
+        else {
+            throw std::logic_error{"unknown input: " + input};
+        }
+    }
+    return info;
+}
+
+void printHelp()
+{
+    std::cerr << "\nUsage:\n"
+    << "The program requires 2 args: (part1, part2) and the path to the file."
+    << "\nFor example, ./day7 part1 data/day7.txt";
+}
+
+int main(int argc, char* argv[])
+{
+    if(argc != 3) {
+        printHelp();
+        return 1;
+    }
+
+    std::string_view task{argv[1]};
+    if(task != "part1" && task != "part2") {
+        std::cerr << "\nfirst arg can be either `part1` or `part2`\n";
+        printHelp();
+        return 1;
+    }
+    
+    std::vector<RobotInfo> inputVec;
+    readInput(argv[2], std::back_inserter(inputVec), parseRobotInfo);
+    
+    if(task == "part1") {
+        std::cout << solveFirstPart(inputVec);
+    }
+    else {
+        std::cout << solveSecondPart(inputVec);
+    }
+
+    return 0;
+}