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This commit is contained in:
Eric Mertens
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a6b6ea5ed0
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a5fe5c007f
153
2022/13.cpp
153
2022/13.cpp
@ -18,83 +18,99 @@ namespace {
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namespace phx = boost::phoenix;
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namespace qi = boost::spirit::qi;
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struct Tree;
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using Trees = std::vector<Tree>;
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using Input = std::vector<std::array<Tree, 2>>;
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struct Packet;
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using Packets = std::vector<Packet>;
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using PacketPair = std::array<Packet, 2>;
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using PacketPairs = std::vector<PacketPair>;
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struct Tree {
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std::variant<std::int64_t, Trees> rep;
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// A packet is an integer or a list of packets.
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struct Packet {
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std::variant<std::int64_t, Packets> rep;
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};
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auto operator<(Tree const& x, std::int64_t y) -> bool;
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auto operator<(std::int64_t x, Tree const& y) -> bool;
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auto operator<(Packet const& lhs, std::int64_t rhs) -> bool;
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auto operator<(std::int64_t lhs, Packet const& rhs) -> bool;
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auto operator<(std::int64_t x, Trees const& y) -> bool {
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switch (y.size()) {
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auto operator<(std::int64_t const lhs, Packets const& rhs) -> bool {
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switch (rhs.size()) {
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case 0: return false;
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case 1: return x < y[0];
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default: return !(y[0] < x);
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case 1: return lhs < rhs[0];
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default: return !(rhs[0] < lhs);
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}
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}
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auto operator<(Trees const& x, std::int64_t y) -> bool {
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switch (x.size()) {
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auto operator<(Packets const& lhs, std::int64_t const rhs) -> bool {
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switch (lhs.size()) {
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case 0: return true;
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default: return x[0] < y;
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default: return lhs[0] < rhs;
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}
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}
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auto operator<(Tree const& x, std::int64_t y) -> bool {
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return std::visit([y](auto const& x_) { return x_ < y; }, x.rep);
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auto operator<(Packet const& lhs, std::int64_t rhs) -> bool {
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return std::visit([rhs](auto const& rep) { return rep < rhs; }, lhs.rep);
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}
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auto operator<(std::int64_t x, Tree const& y) -> bool {
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return std::visit([x](auto const& y_) { return x < y_; }, y.rep);
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auto operator<(std::int64_t lhs, Packet const& rhs) -> bool {
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return std::visit([lhs](auto const& rep) { return lhs < rep; }, rhs.rep);
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}
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auto operator<(Tree const& lhs, Tree const& rhs) -> bool {
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// Less-than relation on packets.
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// Two integers are compared using their integer values.
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// Two lists are compared using a lexicographic ordering.
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// When an integer is compared to a list, that integer is promoted to a singleton list.
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auto operator<(Packet const& lhs, Packet const& rhs) -> bool {
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return std::visit(std::less(), lhs.rep, rhs.rep);
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}
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// Input file grammar:
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// Each packet should be newline-terminated.
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// Each pair should be newline-separated.
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// Packets can be integer literals or a list of packets.
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// A list of packets is bracketed with square brackets and is comma-separated.
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// No additional whitespace is tolerated in the input stream.
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template <typename It>
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class Grammar : public qi::grammar<It, Input()> {
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qi::rule<It, std::int64_t> leaf;
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qi::rule<It, Trees()> trees;
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qi::rule<It, Tree()> tree;
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qi::rule<It, std::array<Tree, 2>()> treepair;
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qi::rule<It, Input()> input;
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class Grammar : public qi::grammar<It, PacketPairs()> {
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qi::rule<It, std::int64_t> integer;
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qi::rule<It, Packets()> packets;
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qi::rule<It, Packet()> packet;
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qi::rule<It, PacketPair()> packetPair;
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qi::rule<It, PacketPairs()> packetPairs;
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public:
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Grammar() : Grammar::base_type{input} {
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Grammar() : Grammar::base_type{packetPairs} {
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using namespace qi::labels;
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leaf = qi::long_long;
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trees = "[" >> -(tree % ",") >> "]";
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tree = leaf [ bind(&Tree::rep, _val) = _1 ]
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| trees [ bind(&Tree::rep, _val) = _1 ];
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treepair = (tree >> "\n" >> tree >> "\n") [(_val[0] = _1, _val[1] = _2)];
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input = -(treepair % "\n");
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integer = qi::long_long;
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packets = "[" >> -(packet % ",") >> "]";
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packet = integer [ bind(&Packet::rep, _val) = _1 ]
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| packets [ bind(&Packet::rep, _val) = _1 ];
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packetPair = packet [_val[0] = _1] >> "\n" >>
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packet [_val[1] = _1] >> "\n";
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packetPairs = -(packetPair % "\n");
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}
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};
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auto Parse(std::istream & in) -> Input
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/// Parse the complete input stream according to the rules defined in 'Grammar'.
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/// Throws: std::runtime_error on failed parse
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auto Parse(std::istream & in) -> PacketPairs
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{
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Input result;
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std::string content {std::istreambuf_iterator{in}, {}};
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auto b {content.begin()};
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auto const e {content.end()};
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auto result = PacketPairs{};
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auto const content = std::string{std::istreambuf_iterator{in}, {}};
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auto b = content.begin(); // updated on successful parse
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auto const e = content.end();
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if (!qi::parse(b, e, Grammar<decltype(b)>{}, result) || b != e) {
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throw std::runtime_error{"tree parser failed"};
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throw std::runtime_error{"Bad packet: " + content};
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}
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return result;
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}
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auto Part1(Input const& input) -> std::size_t
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// Return the sum 1-based indexes of the pairs where the first element is less than the second.
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auto Part1(PacketPairs const& packetPairs) -> std::size_t
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{
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std::int64_t result {0};
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for (auto const& [i,pair] : boost::adaptors::index(input)) {
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auto result = std::int64_t{0};
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for (auto const& [i, pair] : boost::adaptors::index(packetPairs)) {
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if (pair[0] < pair[1]) {
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result += i + 1;
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}
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@ -102,15 +118,20 @@ auto Part1(Input const& input) -> std::size_t
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return result;
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}
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auto Part2(Input const& input) -> std::size_t
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// Returns the product of the 1-based indexes of the elements [[2]] and [[6]]
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// when those elements are added to all the packets in the packet pair list
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// and that list is then soted.
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auto Part2(PacketPairs const& packetPairs) -> std::size_t
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{
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Tree two{2}, six{6}; // Indistinguishable from [[2]] and [[6]]
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std::size_t ix2{1}, ix6{2};
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for (auto const& pair : input) {
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for (auto const& tree : pair) {
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if (tree < six) {
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auto two = Packet{2}; // Indistinguishable from [[2]] and [[6]]
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auto six = Packet{6};
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auto ix2 = std::size_t{1};
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auto ix6 = std::size_t{2};
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for (auto const& pair : packetPairs) {
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for (auto const& Packet : pair) {
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if (Packet < six) {
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ix6++;
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if (tree < two) {
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if (Packet < two) {
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ix2++;
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}
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}
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@ -123,20 +144,20 @@ auto Part2(Input const& input) -> std::size_t
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TEST_SUITE("2022-13 examples") {
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TEST_CASE("simple ordering") {
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CHECK(Tree{1} < Tree{2});
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CHECK(!(Tree{2} < Tree{1}));
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CHECK(Tree{Trees{Tree{1}}} < Tree{Trees{Tree{2}}});
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CHECK(Tree{1} < Tree{Trees{Tree{2}}});
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CHECK(!(Tree{Trees{Tree{2}}} < Tree{1}));
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CHECK(Tree{Trees{}} < Tree{Trees{Tree{2}}});
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CHECK(Tree{Trees{}} < Tree{Trees{Tree{2}}});
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CHECK(Tree{1} < Tree{Trees{Tree{2},Tree{3}}});
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CHECK(!(Tree{Trees{Tree{2},Tree{3}}} < Tree{1}));
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CHECK(Tree{2} < Tree{Trees{Tree{2},Tree{3}}});
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CHECK(!(Tree{Trees{Tree{2},Tree{3}}} < Tree{2}));
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CHECK(Packet{1} < Packet{2});
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CHECK(!(Packet{2} < Packet{1}));
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CHECK(Packet{Packets{Packet{1}}} < Packet{Packets{Packet{2}}});
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CHECK(Packet{1} < Packet{Packets{Packet{2}}});
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CHECK(!(Packet{Packets{Packet{2}}} < Packet{1}));
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CHECK(Packet{Packets{}} < Packet{Packets{Packet{2}}});
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CHECK(Packet{Packets{}} < Packet{Packets{Packet{2}}});
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CHECK(Packet{1} < Packet{Packets{Packet{2},Packet{3}}});
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CHECK(!(Packet{Packets{Packet{2},Packet{3}}} < Packet{1}));
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CHECK(Packet{2} < Packet{Packets{Packet{2},Packet{3}}});
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CHECK(!(Packet{Packets{Packet{2},Packet{3}}} < Packet{2}));
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}
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TEST_CASE("documented example") {
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std::istringstream in {
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auto in = std::istringstream{
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"[1,1,3,1,1]\n"
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"[1,1,5,1,1]\n"
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"\n"
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@ -161,15 +182,15 @@ TEST_SUITE("2022-13 examples") {
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"[1,[2,[3,[4,[5,6,7]]]],8,9]\n"
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"[1,[2,[3,[4,[5,6,0]]]],8,9]\n"
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};
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auto const input = Parse(in);
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CHECK(13 == Part1(input));
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CHECK(140 == Part2(input));
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auto const PacketPairs = Parse(in);
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CHECK(13 == Part1(PacketPairs));
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CHECK(140 == Part2(PacketPairs));
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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 = Parse(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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auto const PacketPairs = Parse(in);
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out << "Part 1: " << Part1(PacketPairs) << std::endl;
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out << "Part 2: " << Part2(PacketPairs) << std::endl;
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}
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