Add 2017 day 7 puzzles

2017/puzzle-07-01.cc

@@ -0,0 +1,60 @@
+#include <iostream>
+#include <map>
+#include <regex>
+#include <set>
+#include <string>
+#include <vector>
+
+using UInt = unsigned long;
+
+auto main() -> int
+{
+  static std::regex top_re{R"(^([a-z]+) \((\d+)\)$)"};
+  static std::regex node_re{R"(^([a-z]+) \((\d+)\) -> (.+)$)"};
+
+  std::string line;
+  std::map<std::string, UInt> weights;
+  std::set<std::string> children_nodes;
+  std::set<std::string> maybe_root;
+
+  while (std::getline(std::cin, line) && !line.empty()) {
+    std::smatch m;
+    if (std::regex_search(line, m, node_re)) {
+      auto weight{std::stoul(m.str(2))};
+      auto node{m.str(1)};
+      auto children{m.str(3)};
+      weights.insert({node, weight});
+      maybe_root.insert(node);
+      std::size_t idx{0};
+      while (idx < children.size()) {
+        if (children[idx] == ' ' || children[idx] == ',') {
+          ++idx;
+          continue;
+        }
+
+        std::string child;
+        while (idx < children.size() && children[idx] != ',') {
+          child.push_back(children[idx]);
+          ++idx;
+        }
+        children_nodes.insert(child);
+      }
+    }
+    else if (std::regex_search(line, m, top_re)) {
+      auto weight{std::stoul(m.str(2))};
+      auto const& node{m.str(1)};
+      weights.insert({node, weight});
+      children_nodes.insert(node);
+    }
+  }
+
+  std::set<std::string> root;
+  std::set_difference(maybe_root.begin(), maybe_root.end(), children_nodes.begin(),
+                      children_nodes.end(), std::inserter(root, root.end()));
+  std::string prefix = "Root = ";
+  for (auto const& n : root) {
+    std::cout << prefix << n;
+    prefix = ", ";
+  }
+  std::cout << '\n';
+}