Initial commit

2020/puzzle-07-02.cc

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+#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 Edge = std::pair<Node, Node>;
+using Weight = unsigned;
+using EdgeWeights = std::map<Edge, Weight>;
+
+struct BagGraph {
+  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 n1 = prefix_m.str(1);
+    std::string suffix = prefix_m.suffix();
+    while (!suffix.empty()) {
+      if (suffix == empty_str) {
+        std::cout << n1 << " -> none: <empty>\n";
+        suffix.clear();
+      } 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 n2 = suffix_m.str(2);
+        suffix = suffix_m.suffix();
+        Edge e = std::make_pair(n1, n2);
+        edges_.insert({e, w});
+        std::cout << n1 << " -> " << n2 << ": " << w << "\n";
+      }
+    }
+  }
+
+  Weight num_contained(Node const &n) {
+    // Get the number of bags including the node we've been asked for so the
+    // result is 1 less than the internal result
+    return num_contained1(n) - 1;
+  }
+
+private:
+  Weight num_contained1(Node const &n) {
+    Weight w = 0;
+    bool contains_something = false;
+    for (auto const &kv : edges_) {
+      if (kv.first.first == n) {
+        w += kv.second * num_contained1(kv.first.second);
+        contains_something = true;
+      }
+    }
+    return w + 1;
+  }
+
+  EdgeWeights edges_;
+};
+
+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 contained = bg.num_contained(n);
+  std::cout << n << " contains " << contained << " bags.\n";
+
+  return 0;
+}