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