150 lines
3.6 KiB
C++
150 lines
3.6 KiB
C++
#include <cstdint>
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#include <iostream>
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#include <set>
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#include <sstream>
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#include <tuple>
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#include <vector>
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#include <variant>
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#include <doctest.h>
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#include <aocpp/Startup.hpp>
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namespace {
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struct Tree {
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std::variant<std::int64_t, std::vector<Tree>> var;
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auto operator<(Tree const& rhs) const -> bool {
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if (var.index() == 0) {
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if (rhs.var.index() == 0) {
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return std::get<0>(var) < std::get<0>(rhs.var);
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} else {
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return Tree{std::vector{*this}} < rhs;
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}
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} else {
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if (rhs.var.index() == 0) {
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return *this < Tree{std::vector{rhs}};
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} else {
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return std::get<1>(var) < std::get<1>(rhs.var);
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}
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}
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}
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};
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using Input = std::vector<Tree>;
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auto ParseTree(std::string::iterator & begin, std::string::iterator end) -> Tree
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{
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if (*begin == '[') {
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begin++;
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if (*begin == ']') {
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begin++;
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return Tree{std::vector<Tree>{}};
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}
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std::vector<Tree> subtrees;
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top: subtrees.emplace_back(ParseTree(begin, end));
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switch (*begin++) {
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case ',': goto top;
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case ']': return Tree{std::move(subtrees)};
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default: throw std::runtime_error{"bad tree list"};
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}
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} else if (isdigit(*begin)) {
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auto number_end = std::find_if_not(begin, end, isdigit);
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std::string number_str {begin, number_end};
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begin = number_end;
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std::int64_t number = std::stoll(number_str);
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return Tree{number};
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} else {
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throw std::runtime_error{"bad tree start"};
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}
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}
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auto Parse(std::istream & in) -> Input
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{
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Input result;
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std::string line;
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while (std::getline(in, line)) {
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auto cursor = line.begin();
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result.push_back(ParseTree(cursor, line.end()));
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std::getline(in, line);
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cursor = line.begin();
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result.push_back(ParseTree(cursor, line.end()));
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std::getline(in, line); // skip blank
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}
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return result;
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}
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auto Part1(Input const& input) -> std::int64_t
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{
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std::int64_t result {0};
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for (std::size_t i = 0; i < input.size(); i += 2) {
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if (input[i] < input[i+1]) {
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result += i/2 + 1;
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}
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}
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return result;
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}
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auto Part2(Input input) -> std::int64_t
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{
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Tree two {std::vector{Tree{std::vector{Tree{2}}}}};
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Tree six {std::vector{Tree{std::vector{Tree{6}}}}};
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auto ix2 = std::count_if(input.begin(), input.end(), [&](auto x) { return x < two; });
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auto ix6 = std::count_if(input.begin(), input.end(), [&](auto x) { return x < six; });
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return (ix2+1) * (ix6+2);
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}
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} // namespace
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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{std::vector{Tree{1}}} < Tree{std::vector{Tree{2}}});
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CHECK(Tree{1} < Tree{std::vector{Tree{2}}});
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CHECK(!(Tree{std::vector{Tree{2}}} < Tree{1}));
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CHECK(Tree{std::vector<Tree>{}} < Tree{std::vector{Tree{2}}});
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CHECK(Tree{std::vector<Tree>{}} < Tree{std::vector{Tree{2}}});
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}
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TEST_CASE("documented example") {
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std::istringstream in {
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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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"[[1],[2,3,4]]\n"
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"[[1],4]\n"
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"\n"
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"[9]\n"
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"[[8,7,6]]\n"
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"\n"
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"[[4,4],4,4]\n"
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"[[4,4],4,4,4]\n"
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"\n"
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"[7,7,7,7]\n"
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"[7,7,7]\n"
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"\n"
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"[]\n"
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"[3]\n"
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"\n"
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"[[[]]]\n"
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"[[]]\n"
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"\n"
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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 input = Parse(in);
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CHECK(13 == Part1(input));
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CHECK(140 == Part2(input));
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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 input = Parse(in);
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out << "count " << input.size() << std::endl;
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out << "Part 1: " << Part1(input) << std::endl;
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out << "Part 2: " << Part2(std::move(input)) << std::endl;
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}
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