Day 14

d14/main.cxx

@@ -1,15 +1,163 @@
+#include <string>
+#include <sstream>
+#include <chrono>
 #include <iostream>
-#include <fstream>
+#include <vector>
+#include <ranges>
+#include <algorithm>
+#include <unordered_map>
+#include <numeric>
 
-using std::cout, std::endl;
+using std::cout, std::endl, std::pair;
 
-int main() {
-    std::ifstream file{"../d14/input.txt"};
+namespace views = std::ranges::views;
+
+constexpr const char content[] = {
+    #embed "input.txt"
+};
+
+namespace std {
+    template<>
+    struct hash<pair<int, int>> {
+        std::size_t operator()(const pair<int, int>& p) const {
+            return std::hash<int>{}(p.first) ^ std::hash<int>{}(p.second);
+        }
+    };
+}
+constexpr auto height{103};
+constexpr auto width{101};
+
+struct Robot {
+    pair<int, int> pos;
+    pair<int, int> velocity;
+};
+
+void move_robot(Robot& r, int time) {
+    r.pos.first = (r.pos.first + time * r.velocity.first) % width;
+    r.pos.second = (r.pos.second + time * r.velocity.second) % height;
+
+    if(r.pos.first < 0) {
+        r.pos.first = width + r.pos.first;
+    }
+
+    if(r.pos.second < 0) {
+        r.pos.second = height + r.pos.second;
+    } 
+}
+
+std::optional<int> get_quadrant(const pair<int, int>& p) {
+    if(p.first == width / 2 || p.second == height / 2) {
+        return std::nullopt;
+    }
+
+    if(p.first <= width / 2 && p.second <= height / 2) {
+        return 0;
+    } else if(p.first > width / 2 && p.second <= height / 2) {
+        return 1;
+    } else if(p.first <= width / 2 && p.second > height / 2) {
+        return 2;
+    } else {
+        return 3;
+    }
+
+}
+
+int64_t part_1() {
+    std::istringstream input_stream(content);
     std::string line;
+    std::vector<Robot> robots = {};
 
-    while (std::getline(file, line)) {
+    while(getline(input_stream, line)) {
+        if(line.empty()) {
+            continue;
+        }
+        std::replace_if(line.begin(), line.end(), [](char c) { return !std::isdigit(c) && c != '-'; }, ' ');
+        Robot r;
+        std::istringstream iss(line);
+        iss >> r.pos.first >> r.pos.second >> r.velocity.first >> r.velocity.second;
+        robots.push_back(r);
+    } 
+
+    std::vector<int> quadrant_count(4, 0);
+    constexpr auto time{100};
+    for(auto& r : robots) {
+        move_robot(r, time);
+        auto q = get_quadrant(r.pos);
+        if(q.has_value()) {
+            quadrant_count[q.value()]++;
+        }
+    }
+
+    auto safety_factor = std::accumulate(quadrant_count.begin(), quadrant_count.end(), 1, std::multiplies<int>());
+    return safety_factor;
+}
+ 
+void print_robots(const std::vector<Robot>& robots) {
+    std::unordered_map<pair<int, int>, char> grid;
+    for(auto& r : robots) {
+        grid[r.pos] = '#';
+    }
+
+    for(auto i = 0; i < height; i++) {
+        for(auto j = 0; j < width; j++) {
+            if(grid.contains({j, i})) {
+                cout << grid[{j, i}];
+            } else {
+                cout << '.';
+            }
+        }
+        cout << endl;
+    }
+}
+
+int64_t part_2() {
+    std::istringstream input_stream(content);
+    std::string line;
+    std::vector<Robot> robots = {};
+
+    while(getline(input_stream, line)) {
+        if(line.empty()) {
+            continue;
+        }
+        std::replace_if(line.begin(), line.end(), [](char c) { return !std::isdigit(c) && c != '-'; }, ' ');
+        Robot r;
+        std::istringstream iss(line);
+        iss >> r.pos.first >> r.pos.second >> r.velocity.first >> r.velocity.second;
+        robots.push_back(r);
+    } 
+
+    auto time_to_tree = 0; // (ttt)
+    while(true) {
+        time_to_tree++;
+        for(auto& r : robots) {
+            move_robot(r, 1);
+        }
+       
+        auto count = 0;
+        for(auto& r : robots) {
+            count = std::count_if(robots.begin(), robots.end(), [&r](const Robot& r2) {
+                return std::abs(r.pos.first - r2.pos.first) <= 2 && std::abs(r.pos.second - r2.pos.second) <= 2;
+            });
+        }
+    
+        // for my input 20 was the magic number 
+        if(count >= 20) {
+            print_robots(robots);
+            break;
+        }
 
     }
     
+    return time_to_tree;
+}
+
+int main() {
+    std::chrono::steady_clock::time_point begin = std::chrono::steady_clock::now();
+    auto p1_val = part_1();
+    std::chrono::steady_clock::time_point middle = std::chrono::steady_clock::now();
+    auto p2_val = part_2();
+    std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();
+    cout << "Part 1: " << p1_val << " (" << std::chrono::duration_cast<std::chrono::microseconds>(middle - begin).count() << "µs)" << endl;  
+    cout << "Part 2: " << p2_val << " (" << std::chrono::duration_cast<std::chrono::microseconds>(end - middle).count() << "µs)" << endl;
     return 0;
 }