82 lines
2.1 KiB
C++
82 lines
2.1 KiB
C++
#include <cassert>
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#include <iostream>
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#include <limits>
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#include <string>
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#include <vector>
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using UInt = unsigned int;
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struct Cost
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{
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constexpr explicit Cost(UInt entry_cost) : entry_cost_(entry_cost) {}
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[[nodiscard]] constexpr auto entry_cost() const noexcept -> UInt { return entry_cost_; }
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[[nodiscard]] constexpr auto total_cost() const noexcept -> UInt { return total_cost_; }
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[[nodiscard]] constexpr auto visited() const noexcept -> bool { return visited_; }
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constexpr void total_cost(UInt total_cost) noexcept { total_cost_ = total_cost; }
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constexpr void update_total_cost(UInt v) noexcept
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{
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total_cost_ = std::min(entry_cost_ + v, total_cost_);
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}
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constexpr void visit() noexcept { visited_ = true; }
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private:
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UInt entry_cost_;
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UInt total_cost_{std::numeric_limits<UInt>::max()};
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bool visited_{false};
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};
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using CostVector = std::vector<Cost>;
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auto main() -> int
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{
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std::string line;
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CostVector costs;
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UInt width{0};
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while (std::getline(std::cin, line) && !line.empty()) {
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if (width == 0) {
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width = line.size();
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}
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else {
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assert(width == line.size());
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}
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for (auto c : line) {
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costs.emplace_back(c - '0');
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}
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}
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costs[0].total_cost(0);
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while (true) {
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/* Note that the comparison below makes deliberate use of unsigned wrap-round. */
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auto it{costs.begin()};
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UInt cost{std::numeric_limits<UInt>::max()};
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for (auto it2{costs.begin()}; it2 != costs.end(); ++it2) {
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if (!it2->visited() && it2->total_cost() < cost) {
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cost = it2->total_cost();
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it = it2;
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}
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}
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it->visit();
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auto current_cost{it->total_cost()};
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auto idx{std::distance(costs.begin(), it)};
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if (idx == costs.size() - 1) {
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std::cout << "Total cost: " << current_cost;
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return 0;
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}
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if (idx % width != 0) {
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costs.at(idx - 1).update_total_cost(current_cost);
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}
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if ((idx + 1) % width != 0) {
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costs.at(idx + 1).update_total_cost(current_cost);
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}
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if (idx > width) {
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costs.at(idx - width).update_total_cost(current_cost);
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}
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if (idx + width < costs.size()) {
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costs.at(idx + width).update_total_cost(current_cost);
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}
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}
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}
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