115 lines
2.5 KiB
C++
115 lines
2.5 KiB
C++
//
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// Created by Matthew Gretton-Dann on 06/12/2021.
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//
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#include <iostream>
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#include <set>
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#include <string>
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using Num = unsigned long;
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struct Node
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{
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Node(Num x, Num y, Num cost) : x_(x), y_(y), cost_(cost) {}
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auto operator==(Node const& rhs) const noexcept -> bool { return x_ == rhs.x_ && y_ == rhs.y_; }
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auto operator<(Node const& rhs) const noexcept -> bool
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{
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return x_ < rhs.x_ || (x_ == rhs.x_ && y_ < rhs.y_);
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}
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Num x() const noexcept { return x_; }
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Num y() const noexcept { return y_; }
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Num cost() const noexcept { return cost_; }
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Node move_left() { return {x_ - 1, y_, cost_ + 1}; }
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Node move_up() { return {x_, y_ + 1, cost_ + 1}; }
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Node move_right() { return {x_ + 1, y_, cost_ + 1}; }
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Node move_down() { return {x_, y_ - 1, cost_ + 1}; }
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private:
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Num x_;
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Num y_;
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Num cost_;
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};
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auto is_wall(Num num, Node const& node)
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{
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Num value{num + node.x() * node.x() + 3 * node.x() + 2 * node.x() * node.y() + node.y() +
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node.y() * node.y()};
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Num bit_count{0};
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while (value != 0) {
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bit_count += value & 1;
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value >>= 1;
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}
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return ((bit_count & 1) == 1) ? true : false;
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}
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struct CostCompare
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{
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constexpr auto operator()(Node const& lhs, Node const& rhs) const noexcept -> bool
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{
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return lhs.cost() < rhs.cost();
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}
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};
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using ToVisitSet = std::multiset<Node, CostCompare>;
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using VisitedSet = std::set<Node>;
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void update_to_visit(ToVisitSet& to_visit, VisitedSet const& visited, Num key, Node const& n)
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{
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if (is_wall(key, n)) {
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return;
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}
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if (visited.contains(n)) {
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return;
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}
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auto it{std::find(to_visit.begin(), to_visit.end(), n)};
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if (it == to_visit.end()) {
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to_visit.insert(n);
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}
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else if (n.cost() < it->cost()) {
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to_visit.erase(it);
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to_visit.insert(n);
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}
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}
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auto main() -> int
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{
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VisitedSet visited;
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ToVisitSet to_visit;
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std::string line;
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if (!std::getline(std::cin, line)) {
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std::cerr << "Unable to read line.\n";
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return 1;
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}
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Num key{std::stoul(line)};
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to_visit.insert(Node{1, 1, 0});
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while (!to_visit.empty()) {
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auto it{to_visit.begin()};
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Node n(*it);
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if (n.x() == 31 && n.y() == 39) {
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std::cout << "Cost = " << n.cost();
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return 0;
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}
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to_visit.erase(it);
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visited.insert(n);
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if (n.x() > 0) {
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update_to_visit(to_visit, visited, key, n.move_left());
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}
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if (n.y() > 0) {
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update_to_visit(to_visit, visited, key, n.move_down());
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}
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update_to_visit(to_visit, visited, key, n.move_right());
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update_to_visit(to_visit, visited, key, n.move_up());
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}
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std::cout << "No solution.\n";
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return 1;
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} |