Initial commit

2015/puzzle-09-02.cc

@@ -0,0 +1,96 @@
+#include <cassert>
+#include <functional>
+#include <iostream>
+#include <map>
+#include <regex>
+#include <set>
+#include <string>
+#include <variant>
+
+using Weight = unsigned;
+using Node = std::string;
+using Edge = std::pair<Node, Node>;
+using Nodes = std::set<Node>;
+using Edges = std::map<Edge, Weight>;
+
+struct Graph {
+  void add_edge(std::string const &s) {
+    static const std::regex re("(.+) to (.+) = (\\d+)");
+    std::smatch m;
+    if (!std::regex_search(s, m, re)) {
+      std::cout << "Failed to match: " << s << "\n";
+      assert(false);
+      return;
+    }
+    auto n1 = m.str(1);
+    auto n2 = m.str(2);
+    auto w = std::stoul(m.str(3));
+    auto edge = std::make_pair(n1, n2);
+    auto back_edge = std::make_pair(n2, n1);
+
+    nodes_.insert(n1);
+    nodes_.insert(n2);
+    weights_.insert({edge, w});
+    weights_.insert({back_edge, w});
+    std::cout << n1 << " <-> " << n2 << " weight: " << w << "\n";
+  }
+
+  Weight solve_tsp() const {
+    Weight min_weight = ~0U;
+    visit_all_perms([&min_weight](Weight w) {
+      if (w < min_weight) {
+        std::cout << "\nNew minimum weight: " << w << "\n";
+        min_weight = w;
+      }
+    });
+    return min_weight;
+  }
+
+  Weight solve_max_tsp() const {
+    Weight max_weight = 0;
+    visit_all_perms([&max_weight](Weight w) {
+      if (w > max_weight) {
+        std::cout << "\nNew maximum weight: " << w << "\n";
+        max_weight = w;
+      }
+    });
+    return max_weight;
+  }
+
+private:
+  template <typename Fn> void visit_all_perms(Fn fn) const {
+    std::vector<Node> nodes(nodes_.begin(), nodes_.end());
+    std::sort(nodes.begin(), nodes.end());
+    do {
+      Weight current_weight = 0;
+      std::cout << "\r" << nodes[0];
+      for (std::size_t i = 1; i < nodes.size(); ++i) {
+        std::cout << " <- " << nodes[i] << std::flush;
+        Edge e = std::make_pair(nodes[i - 1], nodes[i]);
+        auto it = weights_.find(e);
+        assert(it != weights_.end());
+        current_weight += it->second;
+      }
+      std::cout << "         " << std::flush;
+      fn(current_weight);
+    } while (std::next_permutation(nodes.begin(), nodes.end()));
+    std::cout << "\n";
+  }
+  Nodes nodes_;
+  Edges weights_;
+};
+
+int main(int argc, char **argv) {
+  Graph g;
+
+  // Parse the input
+  for (std::string line; std::getline(std::cin, line);) {
+    g.add_edge(line);
+  }
+
+  auto w = g.solve_tsp();
+  std::cout << "Minimum weight = " << w << "\n";
+  w = g.solve_max_tsp();
+  std::cout << "Maximum weight = " << w << "\n";
+  return 0;
+}