From 56288c6ed38ec7416e2b6bc8913c07021ea2c094 Mon Sep 17 00:00:00 2001
From: Eric Mertens <emertens@gmail.com>
Date: Wed, 9 Nov 2022 23:18:43 -0800
Subject: [PATCH] 18p1

---
 2019/18.cpp         | 157 ++++++++++++++++++++++++++++++++++++++++++++
 2019/CMakeLists.txt |   5 +-
 2 files changed, 161 insertions(+), 1 deletion(-)
 create mode 100644 2019/18.cpp

diff --git a/2019/18.cpp b/2019/18.cpp
new file mode 100644
index 0000000..05f6d74
--- /dev/null
+++ b/2019/18.cpp
@@ -0,0 +1,157 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <iomanip>
+#include <fstream>
+#include <iterator>
+#include <stdexcept>
+#include <vector>
+#include <set>
+#include <string>
+#include <tuple>
+#include <bitset>
+#include <deque>
+#include <cctype>
+#include <map>
+
+#include <aocpp/Startup.hpp>
+#include <aocpp/Coord.hpp>
+
+// lowercase key
+// uppercase door
+// start at @
+// wall #
+// boring .
+
+namespace {
+
+using namespace aocpp;
+using Map = std::vector<std::string>;
+using Features = std::map<char, Coord>;
+using Doors = std::bitset<26>;
+using Distances = std::map<char,std::map<char, std::pair<std::int64_t, Doors>>>;
+
+auto ReadMap(std::istream & in) -> Map {
+  Map result;
+  std::string line;
+  while (std::getline(in, line)) {
+    result.emplace_back(std::move(line));
+  }
+  return result;
+}
+
+auto FindFeatures(Map const& map) -> Features {
+  std::map<char,Coord> features;
+  for (std::int64_t y = 0; y < map.size(); y++) {
+    for (std::int64_t x = 0; x < map[y].size(); x++) {
+      auto c = map[y][x];
+      switch (c) {
+        default: features[c] = Coord{x,y};
+        case '#':
+        case '.': {}
+      }
+    }
+  }
+  return features;
+}
+
+auto FindDistancesFrom(
+  Map const& map, Features const& features,
+  Distances & distances,
+  char start_letter, Coord start
+) {
+  std::map<char, std::pair<std::int64_t, Doors>> result;
+  std::set<Coord> seen;
+  std::deque<std::tuple<std::int64_t, Coord, Doors>> todo
+    {{0, start, {}}};
+
+  while (!todo.empty()) {
+    auto [steps, here, doors] = todo.front();
+    todo.pop_front();
+    if (seen.insert(here).second) {
+      auto c = map[here.y][here.x];
+      if (c == '#') {
+        continue;
+      }
+      if (c != start_letter && std::islower(c)) {
+        distances[start_letter][c] = {steps, doors};
+        continue;
+      }
+      if (std::isupper(c)) {
+        doors.set(c - 'A');
+      }
+      for (auto && fn : {Up,Down,Left,Right}) {
+        auto here_ = fn(here);
+        todo.push_back({steps+1, here_, doors});
+      }
+    }
+  }
+
+  return result;
+}
+
+auto FindDistances(Map const& map, Features const& features) -> Distances {
+  Distances distances;
+
+  for (auto && [start_letter, start_coord] : features) {
+    if (islower(start_letter) || start_letter == '@') {
+      FindDistancesFrom(map, features, distances, start_letter, start_coord);
+    }
+  }
+
+  return distances;
+}
+
+struct P1S {
+  char location;
+  unsigned long long keys;
+  auto operator<=>(P1S const&) const = default;
+};
+
+auto HasKey(Doors doors, char key) {
+  return doors.test(std::toupper(key) - 'A');
+}
+
+auto SetKey(Doors doors, char key) {
+  return doors.set(std::toupper(key) - 'A');
+}
+
+auto Part1(Distances const& distances) -> std::int64_t {
+  std::set<P1S> seen;
+  std::multimap<std::int64_t, std::pair<char, Doors>> todo
+    {{0, {'@', Doors()}}};
+
+  while (!todo.empty()) {
+    auto it = todo.begin();
+    auto [steps, ld] = *it;
+    auto& [l,keys] = ld;
+    todo.erase(it);
+
+    if (keys.all()) { return steps; }
+
+    if (seen.insert({l,keys.to_ullong()}).second) {
+      auto dit = distances.find(l);
+      if (dit != distances.end()) {
+        for (auto && [next, costneed] : dit->second) {
+          auto [cost, need] = costneed;
+          if ((need & (~keys)).none()) {
+            todo.insert({steps + cost, {next, SetKey(keys, next)}});
+          }
+        }
+      }
+    }
+  }
+
+  throw std::runtime_error{"no solution to part 1"};
+}
+
+} // namespace
+
+auto main(int argc, char** argv) -> int {
+  auto map = ReadMap(Startup(argc, argv));
+  auto features = FindFeatures(map);
+  auto distances = FindDistances(map, features);
+
+  std::cout << "Part 1: " << Part1(distances) << std::endl;
+  //std::cout << "Part 2: " << part2 << std::endl;
+}
diff --git a/2019/CMakeLists.txt b/2019/CMakeLists.txt
index c76d1cf..f91ac7d 100644
--- a/2019/CMakeLists.txt
+++ b/2019/CMakeLists.txt
@@ -35,10 +35,13 @@ add_executable(13 13.cpp)
 target_link_libraries(13 aocpp intcode)
 
 add_executable(14 14.cpp)
-target_link_libraries(14 aocpp)
+target_link_libraries(14 aocpp Boost::boost)
 
 add_executable(15 15.cpp)
 target_link_libraries(15 aocpp intcode)
 
+add_executable(18 18.cpp)
+target_link_libraries(18 aocpp)
+
 add_executable(23 23.cpp)
 target_link_libraries(23 aocpp intcode)