Solutions for 2018 day 13

2018/puzzle-13-01.cc

@@ -0,0 +1,145 @@
+//
+// Created by Matthew Gretton-Dann on 01/12/2022.
+//
+
+#include <array>
+#include <cstdlib>
+#include <iomanip>
+#include <iostream>
+#include <regex>
+#include <set>
+#include <utility>
+
+using Int = std::int64_t;
+using UInt = std::uint64_t;
+using Point = std::pair<Int, Int>;
+
+enum DirSelect {
+  left = 0,
+  straight = 1,
+  right = 2,
+};
+
+constexpr Point north{0, -1};
+constexpr Point east{1, 0};
+constexpr Point south{0, 1};
+constexpr Point west{-1, 0};
+
+struct Truck
+{
+  Point pt_{0, 0};
+  Point dir_{north};
+  std::size_t dir_select_{0};
+  UInt time_stamp_{0};
+
+  constexpr auto operator<(Truck const& r) const noexcept -> bool
+  {
+    return pt_.first < r.pt_.first || (pt_.first == r.pt_.first && pt_.second < r.pt_.second);
+  }
+};
+
+using State = std::set<Truck>;
+
+auto main() -> int
+{
+  std::string line;
+  std::vector<std::string> map;
+  State trucks;
+
+  Point pos{0, 0};
+  while (std::getline(std::cin, line)) {
+    for (auto& c : line) {
+      switch (c) {
+      case '>':
+        trucks.insert({pos, east, 0, 0});
+        c = '-';
+        break;
+      case '<':
+        trucks.insert({pos, west, 0, 0});
+        c = '-';
+        break;
+      case '^':
+        trucks.insert({pos, north, 0, 0});
+        c = '|';
+        break;
+      case 'v':
+        trucks.insert({pos, south, 0, 0});
+        c = '|';
+        break;
+      }
+      pos.first += 1;
+    }
+    map.push_back(line);
+    pos.first = 0;
+    pos.second += 1;
+  }
+
+  UInt time_step{0};
+  while (true) {
+    ++time_step;
+    std::cout << "\n" << std::setw(3) << time_step << ": ";
+    auto truck{trucks.begin()};
+    while (truck != trucks.end()) {
+      if (truck->time_stamp_ >= time_step) {
+        ++truck;
+        continue;
+      }
+      std::cout << truck->pt_.first << "," << truck->pt_.second << ", ";
+      Point dir{truck->dir_};
+      std::size_t dir_select = truck->dir_select_;
+      Point const pos{truck->pt_.first + dir.first, truck->pt_.second + dir.second};
+      auto c{map.at(pos.second).at(pos.first)};
+      switch (c) {
+      case '|':
+      case '-':
+        break;
+      case '/':
+        if (dir == west) {
+          dir = south;
+        }
+        else if (dir == south) {
+          dir = west;
+        }
+        else if (dir == east) {
+          dir = north;
+        }
+        else if (dir == north) {
+          dir = east;
+        }
+        break;
+      case '\\':
+        if (dir == west) {
+          dir = north;
+        }
+        else if (dir == north) {
+          dir = west;
+        }
+        else if (dir == east) {
+          dir = south;
+        }
+        else if (dir == south) {
+          dir = east;
+        }
+        break;
+      case '+':
+        if (dir_select == left) {
+          dir = Point{dir.second, -dir.first};
+        }
+        else if (dir_select == right) {
+          dir = Point{-dir.second, dir.first};
+        }
+        dir_select = (dir_select + 1) % 3;
+        break;
+      default:
+        abort();
+      }
+      Truck const next_truck{pos, dir, dir_select, time_step};
+      truck = trucks.erase(truck);
+      auto [next_it, success] = trucks.insert(next_truck);
+      if (!success) {
+        std::cout << "Crash at: " << pos.first << "," << pos.second << "\n";
+        return EXIT_SUCCESS;
+      }
+    }
+  }
+}

2018/puzzle-13-02.cc

@@ -0,0 +1,149 @@
+//
+// Created by Matthew Gretton-Dann on 01/12/2022.
+//
+
+#include <array>
+#include <cstdlib>
+#include <iomanip>
+#include <iostream>
+#include <regex>
+#include <set>
+#include <utility>
+
+using Int = std::int64_t;
+using UInt = std::uint64_t;
+using Point = std::pair<Int, Int>;
+
+enum DirSelect {
+  left = 0,
+  straight = 1,
+  right = 2,
+};
+
+constexpr Point north{0, -1};
+constexpr Point east{1, 0};
+constexpr Point south{0, 1};
+constexpr Point west{-1, 0};
+
+struct Truck
+{
+  Point pt_{0, 0};
+  Point dir_{north};
+  std::size_t dir_select_{0};
+  UInt time_stamp_{0};
+
+  constexpr auto operator<(Truck const& r) const noexcept -> bool
+  {
+    return pt_.first < r.pt_.first || (pt_.first == r.pt_.first && pt_.second < r.pt_.second);
+  }
+};
+
+using State = std::set<Truck>;
+
+auto main() -> int
+{
+  std::string line;
+  std::vector<std::string> map;
+  State trucks;
+
+  Point pos{0, 0};
+  while (std::getline(std::cin, line)) {
+    for (auto& c : line) {
+      switch (c) {
+      case '>':
+        trucks.insert({pos, east, 0, 0});
+        c = '-';
+        break;
+      case '<':
+        trucks.insert({pos, west, 0, 0});
+        c = '-';
+        break;
+      case '^':
+        trucks.insert({pos, north, 0, 0});
+        c = '|';
+        break;
+      case 'v':
+        trucks.insert({pos, south, 0, 0});
+        c = '|';
+        break;
+      }
+      pos.first += 1;
+    }
+    map.push_back(line);
+    pos.first = 0;
+    pos.second += 1;
+  }
+
+  UInt time_step{0};
+  while (trucks.size() > 1) {
+    ++time_step;
+    std::cout << "\n" << std::setw(3) << time_step << ": ";
+    auto truck{trucks.begin()};
+    while (truck != trucks.end()) {
+      if (truck->time_stamp_ >= time_step) {
+        ++truck;
+        continue;
+      }
+      std::cout << truck->pt_.first << "," << truck->pt_.second << ", ";
+      Point dir{truck->dir_};
+      std::size_t dir_select = truck->dir_select_;
+      Point const pos{truck->pt_.first + dir.first, truck->pt_.second + dir.second};
+      auto c{map.at(pos.second).at(pos.first)};
+      switch (c) {
+      case '|':
+      case '-':
+        break;
+      case '/':
+        if (dir == west) {
+          dir = south;
+        }
+        else if (dir == south) {
+          dir = west;
+        }
+        else if (dir == east) {
+          dir = north;
+        }
+        else if (dir == north) {
+          dir = east;
+        }
+        break;
+      case '\\':
+        if (dir == west) {
+          dir = north;
+        }
+        else if (dir == north) {
+          dir = west;
+        }
+        else if (dir == east) {
+          dir = south;
+        }
+        else if (dir == south) {
+          dir = east;
+        }
+        break;
+      case '+':
+        if (dir_select == left) {
+          dir = Point{dir.second, -dir.first};
+        }
+        else if (dir_select == right) {
+          dir = Point{-dir.second, dir.first};
+        }
+        dir_select = (dir_select + 1) % 3;
+        break;
+      default:
+        abort();
+      }
+      Truck const next_truck{pos, dir, dir_select, time_step};
+      truck = trucks.erase(truck);
+      auto [next_it, success] = trucks.insert(next_truck);
+      if (!success) {
+        std::cout << "Crash at: " << pos.first << "," << pos.second << "\n";
+        trucks.erase(next_it);
+        truck = trucks.begin();
+      }
+    }
+  }
+
+  auto truck(trucks.begin());
+  std::cout << "Point: " << truck->pt_.first << "," << truck->pt_.second << "\n";
+}