2016-01

2016/01.cpp

@@ -0,0 +1,121 @@
+#include <cstdint>
+#include <iostream>
+#include <sstream>
+#include <stdexcept>
+#include <unordered_map>
+#include <vector>
+
+#include <boost/phoenix.hpp>
+#include <boost/range/irange.hpp>
+#include <boost/spirit/include/qi.hpp>
+
+#include <doctest.h>
+
+#include <aocpp/Coord.hpp>
+#include <aocpp/Parsing.hpp>
+#include <aocpp/Startup.hpp>
+
+namespace {
+
+namespace phx = boost::phoenix;
+namespace qi = boost::spirit::qi;
+
+enum class Dir { L, R };
+
+struct Command {
+  Dir dir;
+  std::size_t n;
+};
+
+using Input = std::vector<Command>;
+
+// Input file grammar
+class Grammar : public qi::grammar<std::string::const_iterator, Input(), qi::ascii::space_type> {
+  qi::rule<iterator_type, Dir()> dir;
+  qi::rule<iterator_type, Command(), qi::ascii::space_type> command;
+  qi::rule<iterator_type, Input(), qi::ascii::space_type> commands;
+
+public:
+  Grammar() : Grammar::base_type{commands} {
+    using namespace qi::labels;
+
+    dir =
+      qi::string("L") [ _val = Dir::L ] |
+      qi::string("R") [ _val = Dir::R ];
+    command = qi::lexeme[
+      dir [ phx::bind(&Command::dir, _val) = _1] >>
+      qi::ulong_long [ phx::bind(&Command::n, _val) = _1]
+    ];
+    commands = command % ",";
+  }
+};
+
+auto Part1(Input const& input) -> std::int64_t
+{
+  auto here = aocpp::Coord{};
+  auto face = aocpp::Coord{0,1};
+
+  for (auto const& command : input) {
+    switch (command.dir) {
+      case Dir::R: face = aocpp::CW(face); break;
+      case Dir::L: face = aocpp::CCW(face); break;
+    }
+    here += command.n * face;
+  }
+
+  return aocpp::Norm1(here);
+}
+
+auto Part2(Input const& input) -> std::int64_t
+{
+  auto seen = std::unordered_set<aocpp::Coord>{aocpp::Coord{0,0}};
+  auto here = aocpp::Coord{0,0};
+  auto face = aocpp::Coord{0,1};
+
+  for (auto const& command : input) {
+    switch (command.dir) {
+      case Dir::R: face = aocpp::CW(face); break;
+      case Dir::L: face = aocpp::CCW(face); break;
+    }
+    for (auto const _ : boost::irange(command.n)) {
+      here += face;
+      if (!seen.insert(here).second) {
+        return aocpp::Norm1(here);
+      }
+    }
+  }
+
+  throw std::runtime_error{"no solution to part 2"};
+}
+
+} // namespace
+
+TEST_SUITE("2016-01 examples") {
+  TEST_CASE("example 1") {
+    auto in = std::istringstream{"R2, L3"};
+    auto const commands = aocpp::ParseGrammar_(Grammar{}, in);
+    CHECK(5 == Part1(commands));
+  }
+  TEST_CASE("example 2") {
+    auto in = std::istringstream{"R2, R2, R2"};
+    auto const commands = aocpp::ParseGrammar_(Grammar{}, in);
+    CHECK(2 == Part1(commands));
+  }
+  TEST_CASE("example 3") {
+    auto in = std::istringstream{"R5, L5, R5, R3"};
+    auto const commands = aocpp::ParseGrammar_(Grammar{}, in);
+    CHECK(12 == Part1(commands));
+  }
+  TEST_CASE("example 4") {
+    auto in = std::istringstream{"R8, R4, R4, R8"};
+    auto const commands = aocpp::ParseGrammar_(Grammar{}, in);
+    CHECK(4 == Part2(commands));
+  }
+}
+
+auto Main(std::istream & in, std::ostream & out) -> void
+{
+  auto const input = aocpp::ParseGrammar_(Grammar{}, in);
+  out << "Part 1: " << Part1(input) << std::endl;
+  out << "Part 2: " << Part2(input) << std::endl;
+}

2016/CMakeLists.txt

@@ -0,0 +1,2 @@
+add_executable(2016_01 01.cpp)
+target_link_libraries(2016_01 aocpp Boost::headers)

CMakeLists.txt

@@ -26,6 +26,7 @@ add_subdirectory(dlx)
 add_subdirectory(knothash)
 add_subdirectory(zmod)
 add_subdirectory(intcode)
+add_subdirectory(2016)
 add_subdirectory(2017)
 add_subdirectory(2018)
 add_subdirectory(2019)

lib/include/aocpp/Coord.hpp

@@ -66,6 +66,15 @@ auto operator-=(Coord &, Coord) -> Coord &;
 /// Write a coordinate to a string "(x,y)"
 auto operator<<(std::ostream &, Coord) -> std::ostream &;
 
+/// Scale a coordinate
+auto operator*(std::int64_t, Coord) -> Coord;
+
+/// Scale a coordinate
+auto operator*(Coord, std::int64_t) -> Coord;
+
+/// Scale a coordinate
+auto operator*=(Coord &, std::int64_t) -> Coord &;
+
 } // namespace
 
 template<>

lib/include/aocpp/Parsing.hpp

@@ -30,6 +30,22 @@ auto ParseGrammar(G const& grammar, std::istream & in) -> typename G::start_type
   return result;
 }
 
+template <typename G>
+auto ParseGrammar_(G const& grammar, std::istream & in) -> typename G::start_type::attr_type
+{
+  namespace qi = boost::spirit::qi;
+  auto result = typename G::start_type::attr_type {};
+  auto const content = std::string{std::istreambuf_iterator{in}, {}};
+  auto b = content.begin(); // updated on successful parse
+  auto const e = content.end();
+
+  if (!qi::phrase_parse(b, e, grammar, qi::ascii::space, result) || b != e) {
+    throw std::runtime_error{"Bad input file: " + content};
+  }
+
+  return result;
+}
+
 }
 
 #endif

lib/src/Coord.cpp

@@ -95,6 +95,22 @@ auto operator-=(Coord & a, Coord b) -> Coord & {
   return a;
 }
 
+auto operator*(Coord a, std::int64_t b) -> Coord {
+  return a *= b;
+}
+
+auto operator*(std::int64_t a, Coord b) -> Coord {
+  b.x *= a;
+  b.y *= a;
+  return b;
+}
+
+auto operator*=(Coord & a, std::int64_t b) -> Coord & {
+  a.x *= b;
+  a.y *= b;
+  return a;
+}
+
 auto operator<<(std::ostream & out, Coord c) -> std::ostream & {
   return out << "(" << c.x << "," << c.y << ")";
 }