108 lines
2.1 KiB
C++
108 lines
2.1 KiB
C++
//
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// Created by Matthew Gretton-Dann on 09/12/2022.
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//
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#include <array>
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#include <iostream>
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#include <numeric>
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#include <set>
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#include <string>
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#include <utility>
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using Int = std::int64_t;
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using Pos = std::pair<Int, Int>;
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struct compare_pos
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{
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constexpr auto operator()(Pos const& l, Pos const& r) const noexcept
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{
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if (l.second < r.second) {
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return true;
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}
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if (l.second == r.second && l.first < r.first) {
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return true;
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}
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return false;
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}
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};
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struct State
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{
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State()
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{
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for (auto it{rope_.begin()}; it != rope_.end(); ++it) {
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*it = {0, 0};
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}
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visited_.insert({0, 0});
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}
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auto move(Pos dir, Int steps)
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{
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for (Int i{0}; i != steps; ++i) {
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auto it = rope_.begin();
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it->first += dir.first;
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it->second += dir.second;
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Pos pos{*it};
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while (it != rope_.end()) {
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if (std::abs(it->first - pos.first) > 1 || std::abs(it->second - pos.second) > 1) {
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if (it->first < pos.first) {
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++it->first;
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}
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if (it->first > pos.first) {
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--it->first;
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}
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if (it->second < pos.second) {
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++it->second;
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}
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if (it->second > pos.second) {
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--it->second;
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}
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}
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pos = *it;
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++it;
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}
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visited_.insert(pos);
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}
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}
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[[nodiscard]] auto visited_count() const noexcept { return visited_.size(); }
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std::array<Pos, 10> rope_;
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std::set<Pos, compare_pos> visited_;
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};
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auto main() -> int
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{
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std::string line;
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State state;
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while (std::getline(std::cin, line) && !line.empty()) {
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auto item{line[0]};
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Pos dir{0, 0};
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Int const amount{std::stoll(line.substr(2))};
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switch (item) {
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case 'L':
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dir.first = -1;
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break;
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case 'R':
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dir.first = 1;
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break;
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case 'U':
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dir.second = 1;
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break;
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case 'D':
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dir.second = -1;
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break;
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default:
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std::cerr << "Unable to interpret: " << line << '\n';
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return EXIT_FAILURE;
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}
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state.move(dir, amount);
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}
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std::cout << "Number of locations visited: " << state.visited_count() << '\n';
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return 0;
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}
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