2023 Day 8

2023/puzzle-08-01.cc

@@ -0,0 +1,83 @@
+#include <array>
+#include <cassert>
+#include <compare>
+#include <cstdint>
+#include <cstdlib>
+#include <iostream>
+#include <map>
+#include <string>
+#include <string_view>
+#include <utility>
+
+using UInt = std::uint64_t;
+using Location = std::array<char, 3>;
+using LocationPair = std::pair<Location, Location>;
+
+auto operator<<(std::ostream& os, Location const& cards) -> std::ostream&
+{
+  for (auto const c : cards) { os << c; }
+  return os;
+}
+
+[[nodiscard]] auto operator<=>(Location const& lhs, Location const& rhs) -> std::strong_ordering
+{
+  for (auto lhs_it{lhs.begin()}, rhs_it{rhs.begin()}; lhs_it != lhs.end(); ++lhs_it, ++rhs_it) {
+    if (*lhs_it != *rhs_it) {
+      return *lhs_it <=> *rhs_it;
+    }
+  }
+  return std::strong_ordering::equal;
+}
+
+struct LocationMap
+{
+  void emplace(std::string_view const line)
+  {
+    auto from = Location{line[0], line[1], line[2]};
+    auto left = Location{line[7], line[8], line[9]};
+    auto right = Location{line[12], line[13], line[14]};
+    auto [it, success] = locs_.insert({from, {left, right}});
+    assert(success);
+  }
+
+  std::map<Location, LocationPair> locs_;
+};
+
+auto main() -> int try {
+  std::string line;
+  std::string directions;
+  LocationMap map;
+
+  std::getline(std::cin, directions); /// Directions line
+  std::getline(std::cin, line);       /// Blank line
+
+  while (std::getline(std::cin, line)) {
+    map.emplace(line);
+  }
+
+  UInt steps = 0;
+  auto location = map.locs_.find({'A', 'A', 'A'});
+  auto direction = directions.begin();
+  while (location->first != Location{'Z', 'Z', 'Z'}) {
+    if (*direction == 'L') {
+      location = map.locs_.find(location->second.first);
+    }
+    else if (*direction == 'R') {
+      location = map.locs_.find(location->second.second);
+    }
+    else {
+      std::abort();
+    }
+    ++direction;
+    if (direction == directions.end()) { direction = directions.begin(); }
+    ++steps;
+  }
+
+  std::cout << "Steps: " << steps;
+
+  return EXIT_SUCCESS;
+}
+catch (...) {
+  std::cerr << "Uncaught exception.\n";
+  return EXIT_FAILURE;
+}