84 lines
1.9 KiB
C++
84 lines
1.9 KiB
C++
#include <iostream>
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#include <numeric>
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#include <regex>
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#include <string>
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#include <vector>
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using UInt = unsigned long;
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using Chain = std::pair<UInt, UInt>;
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struct State
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{
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void add(Chain const& chain) { chains_.push_back({chain, false}); }
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template<typename Inserter>
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void next_states(Inserter inserter) const
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{
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State next(*this);
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for (auto& chain : next.chains_) {
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if (chain.second) {
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continue;
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}
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if (chain.first.first == tail_end_) {
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next.tail_end_ = chain.first.second;
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chain.second = true;
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*inserter++ = next;
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}
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if (chain.first.second == tail_end_) {
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next.tail_end_ = chain.first.first;
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chain.second = true;
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*inserter++ = next;
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}
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chain.second = false;
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}
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}
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[[nodiscard]] auto strength() const noexcept -> UInt
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{
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return std::accumulate(chains_.begin(), chains_.end(), UInt{0}, [](UInt a, auto const& c) {
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if (c.second) {
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return a + c.first.first + c.first.second;
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}
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else {
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return a;
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}
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});
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}
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private:
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UInt tail_end_{0};
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std::vector<std::pair<Chain, bool>> chains_;
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};
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auto main() -> int
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{
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std::regex re{"(\\d+)/(\\d+)"};
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std::string line;
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State initial_state;
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while (std::getline(std::cin, line) && !line.empty()) {
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std::smatch m;
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if (!std::regex_search(line, m, re)) {
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std::cerr << "Unable to interpret: " << line << '\n';
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return 1;
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}
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initial_state.add({std::stoul(m.str(1)), std::stoul(m.str(2))});
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}
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auto strength{initial_state.strength()};
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std::vector<State> states;
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states.push_back(initial_state);
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while (!states.empty()) {
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std::vector<State> next_states;
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auto inserter{std::back_inserter(next_states)};
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for (auto const& state : states) {
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strength = std::max(strength, state.strength());
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state.next_states(inserter);
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}
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std::swap(states, next_states);
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}
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std::cout << "Max strength: " << strength << '\n';
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return 0;
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}
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