Initial commit

2020/puzzle-07-01.cc

@@ -0,0 +1,119 @@
+#include <algorithm>
+#include <cassert>
+#include <iostream>
+#include <list>
+#include <map>
+#include <regex>
+#include <string>
+
+// This code is horrible - my only excuse is I wrote it before breakfast
+
+using Node = std::string;
+using Nodes = std::map<Node, bool>;
+using Edge = std::pair<Node, Node>;
+using Weight = unsigned;
+using EdgeWeights = std::map<Edge, Weight>;
+using NodeQueue = std::list<Node>;
+
+std::ostream &operator<<(std::ostream &os, NodeQueue const &q) {
+  std::string p = "";
+  os << "[";
+  for (auto const &n : q) {
+    os << p << n;
+    p = ", ";
+  }
+  os << "]";
+  return os;
+}
+
+struct BagGraph {
+  BagGraph() { nodes_.insert({"", false}); }
+
+  void add_edges(std::string const &s) {
+    static const auto prefix_re = std::regex("([a-z ]+) bags? contain ");
+    static const auto suffix_re = std::regex("(\\d)+ ([a-z ]+) bags?[,.]\\s*");
+    static const auto empty_str = std::string("no other bags.");
+    std::smatch prefix_m;
+    if (!std::regex_search(s, prefix_m, prefix_re)) {
+      std::cout << "Failed to match: " << s << "\n";
+      assert(false);
+      return;
+    }
+
+    std::string n2 = prefix_m.str(1);
+    nodes_.insert({n2, false});
+    std::string suffix = prefix_m.suffix();
+    while (!suffix.empty()) {
+      if (suffix == empty_str) {
+        suffix = "";
+        Edge e = std::make_pair("", n2);
+        edges_.insert({e, 0});
+        std::cout << "<none> -> " << n2 << ": 0\n";
+      } else {
+        std::smatch suffix_m;
+        if (!std::regex_search(suffix, suffix_m, suffix_re)) {
+          std::cout << "Failed to match: " << suffix << "\n";
+          assert(false);
+          return;
+        }
+        Weight w = std::stoul(suffix_m.str(1));
+        Node n1 = suffix_m.str(2);
+        suffix = suffix_m.suffix();
+        Edge e = std::make_pair(n1, n2);
+        nodes_.insert({n1, false});
+        edges_.insert({e, w});
+        std::cout << n1 << " -> " << n2 << ": " << w << "\n";
+      }
+    }
+  }
+
+  unsigned num_containers(Node const &n) {
+    NodeQueue queue;
+    // Initial population of queue:
+    populate_queue(queue, n);
+    std::cout << "Initial queue: " << queue << "\n";
+    unsigned visited = 0;
+
+    // Iterate over queue finding how
+    while (!queue.empty()) {
+      Node n1 = queue.front();
+      std::cout << "Processing: " << n1 << "\n";
+      queue.pop_front();
+      if (!nodes_[n1]) {
+        nodes_[n1] = true;
+        populate_queue(queue, n1);
+        ++visited;
+        std::cout << "Updated queue: " << queue << "\n";
+      } else {
+        std::cout << "Already visited\n";
+      }
+    }
+
+    return visited;
+  }
+
+private:
+  void populate_queue(NodeQueue &queue, Node const &n) {
+    for (auto const &kv : edges_) {
+      if (kv.first.first == n && !nodes_[kv.first.second]) {
+        queue.push_back(kv.first.second);
+      }
+    }
+  }
+
+  EdgeWeights edges_;
+  Nodes nodes_;
+};
+
+int main(int argc, char **argv) {
+  BagGraph bg;
+  for (std::string line; std::getline(std::cin, line);) {
+    bg.add_edges(line);
+  }
+
+  Node n = "shiny gold";
+  auto visited = bg.num_containers(n);
+  std::cout << "Number of " << n << " containers " << visited << "\n";
+
+  return 0;
+}