64 lines
1.4 KiB
C++
64 lines
1.4 KiB
C++
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#include <aocpp/Parsing.hpp>
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#include <aocpp/Startup.hpp>
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#include <boost/tuple/tuple.hpp>
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#include <boost/spirit/include/qi.hpp>
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#include <optional>
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#include <stack>
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namespace qi = boost::spirit::qi;
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namespace {
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auto
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suffixed(std::uint64_t x, std::uint64_t y) -> std::optional<std::uint64_t>
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{
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while (x > 0) {
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if (y == 0) { return x; }
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if (x % 10 != y % 10) { return {}; }
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x /= 10;
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y /= 10;
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}
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return {};
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}
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auto
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check(bool part2, std::uint64_t target, std::vector<std::uint64_t> const& numbers) -> bool
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{
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std::stack<boost::tuple<std::size_t, std::uint64_t>> work;
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work.push({numbers.size() - 1, target});
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while (!work.empty()){
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auto [i, t] = work.top();
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work.pop();
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auto x = numbers[i];
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if (i == 0) {
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if (x == t) return true;
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} else {
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if (x < t) { work.push({i-1, t-x}); }
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if (t % x == 0) { work.push({i-1, t/x}); }
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if (part2) { if (auto u = suffixed(t,x)) { work.push({i-1, *u}); } }
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}
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}
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return false;
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}
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} // namespace
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auto Main(std::istream & in, std::ostream & out) -> void
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{
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std::vector<boost::tuple<std::uint64_t, std::vector<std::uint64_t>>> input;
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aocpp::ParseSimple(in, *(qi::ulong_long >> ":" >> *(" " >> qi::ulong_long) >> "\n"), input);
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std::uint64_t p1{}, p2{};
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for (auto && [x, xs] : input) {
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if (check(false, x, xs)) p1 += x;
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if (check(true, x, xs)) p2 += x;
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}
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out << "Part 1: " << p1 << "\n"
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<< "Part 2: " << p2 << "\n";
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}
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