95 lines
2.1 KiB
C++
95 lines
2.1 KiB
C++
//
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// Created by Matthew Gretton-Dann on 12/12/2021.
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//
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#include <cctype>
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#include <iostream>
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#include <map>
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#include <set>
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#include <string>
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#include <vector>
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using Paths = std::multimap<std::string, std::string>;
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using Route = std::vector<std::string>;
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auto is_upper_case(std::string const& s) -> bool { return std::isupper(s[0]) ? true : false; }
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auto is_visitable(Route const& route, Paths const& paths, std::string const& proposed) -> bool
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{
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if (is_upper_case(proposed)) {
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return true;
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}
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std::set<std::string> visited;
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bool little_visited_twice{false};
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for (auto r : route) {
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if (!is_upper_case(r)) {
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if (visited.contains(r)) {
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little_visited_twice = true;
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break;
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}
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visited.insert(r);
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}
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}
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if (!little_visited_twice) {
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return true;
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}
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auto route_it = std::find(route.begin(), route.end(), proposed);
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return route_it == route.end();
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}
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template<typename Fn>
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void visit(Route& route, Paths const& paths, Fn visitor)
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{
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auto [path_begin, path_end] = paths.equal_range(route.back());
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if (path_begin == path_end) {
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visitor(route, paths);
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return;
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}
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for (auto it{path_begin}; it != path_end; ++it) {
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if (is_visitable(route, paths, it->second)) {
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route.push_back(it->second);
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visit(route, paths, visitor);
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route.pop_back();
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}
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}
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}
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auto main() -> int
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{
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Paths paths;
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std::string line;
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while (std::getline(std::cin, line)) {
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auto sep{line.find('-')};
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auto from{line.substr(0, sep)};
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auto to{line.substr(sep + 1)};
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// Make sure we don't visit start or end more than once.
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if (to == "start") {
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std::swap(from, to);
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}
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if (from == "end") {
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std::swap(from, to);
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}
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paths.insert({from, to});
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if (from != "start" && to != "end") {
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paths.insert({to, from});
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}
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}
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unsigned route_count{0};
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Route route{"start"};
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visit(route, paths, [&route_count](auto const& route, auto const&) {
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for (auto r : route) {
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std::cout << " " << r;
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}
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std::cout << "\n";
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++route_count;
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});
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std::cout << "Routes count: " << route_count;
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return 0;
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}
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