Add 2017 Day 24 puzzles

2017/puzzle-24-01.cc

@@ -0,0 +1,83 @@
+#include <iostream>
+#include <numeric>
+#include <regex>
+#include <string>
+#include <vector>
+
+using UInt = unsigned long;
+using Chain = std::pair<UInt, UInt>;
+
+struct State
+{
+  void add(Chain const& chain) { chains_.push_back({chain, false}); }
+
+  template<typename Inserter>
+  void next_states(Inserter inserter) const
+  {
+    State next(*this);
+    for (auto& chain : next.chains_) {
+      if (chain.second) {
+        continue;
+      }
+      if (chain.first.first == tail_end_) {
+        next.tail_end_ = chain.first.second;
+        chain.second = true;
+        *inserter++ = next;
+      }
+      if (chain.first.second == tail_end_) {
+        next.tail_end_ = chain.first.first;
+        chain.second = true;
+        *inserter++ = next;
+      }
+      chain.second = false;
+    }
+  }
+
+  [[nodiscard]] auto strength() const noexcept -> UInt
+  {
+    return std::accumulate(chains_.begin(), chains_.end(), UInt{0}, [](UInt a, auto const& c) {
+      if (c.second) {
+        return a + c.first.first + c.first.second;
+      }
+      else {
+        return a;
+      }
+    });
+  }
+
+private:
+  UInt tail_end_{0};
+  std::vector<std::pair<Chain, bool>> chains_;
+};
+
+auto main() -> int
+{
+  std::regex re{"(\\d+)/(\\d+)"};
+  std::string line;
+  State initial_state;
+
+  while (std::getline(std::cin, line) && !line.empty()) {
+    std::smatch m;
+    if (!std::regex_search(line, m, re)) {
+      std::cerr << "Unable to interpret: " << line << '\n';
+      return 1;
+    }
+    initial_state.add({std::stoul(m.str(1)), std::stoul(m.str(2))});
+  }
+
+  auto strength{initial_state.strength()};
+  std::vector<State> states;
+  states.push_back(initial_state);
+  while (!states.empty()) {
+    std::vector<State> next_states;
+    auto inserter{std::back_inserter(next_states)};
+    for (auto const& state : states) {
+      strength = std::max(strength, state.strength());
+      state.next_states(inserter);
+    }
+    std::swap(states, next_states);
+  }
+
+  std::cout << "Max strength: " << strength << '\n';
+  return 0;
+}

2017/puzzle-24-02.cc

@@ -0,0 +1,84 @@
+#include <iostream>
+#include <numeric>
+#include <regex>
+#include <string>
+#include <vector>
+
+using UInt = unsigned long;
+using Chain = std::pair<UInt, UInt>;
+
+struct State
+{
+  void add(Chain const& chain) { chains_.push_back({chain, false}); }
+
+  template<typename Inserter>
+  void next_states(Inserter inserter) const
+  {
+    State next(*this);
+    for (auto& chain : next.chains_) {
+      if (chain.second) {
+        continue;
+      }
+      if (chain.first.first == tail_end_) {
+        next.tail_end_ = chain.first.second;
+        chain.second = true;
+        *inserter++ = next;
+      }
+      if (chain.first.second == tail_end_) {
+        next.tail_end_ = chain.first.first;
+        chain.second = true;
+        *inserter++ = next;
+      }
+      chain.second = false;
+    }
+  }
+
+  [[nodiscard]] auto strength() const noexcept -> UInt
+  {
+    return std::accumulate(chains_.begin(), chains_.end(), UInt{0}, [](UInt a, auto const& c) {
+      if (c.second) {
+        return a + c.first.first + c.first.second;
+      }
+      else {
+        return a;
+      }
+    });
+  }
+
+private:
+  UInt tail_end_{0};
+  std::vector<std::pair<Chain, bool>> chains_;
+};
+
+auto main() -> int
+{
+  std::regex re{"(\\d+)/(\\d+)"};
+  std::string line;
+  State initial_state;
+
+  while (std::getline(std::cin, line) && !line.empty()) {
+    std::smatch m;
+    if (!std::regex_search(line, m, re)) {
+      std::cerr << "Unable to interpret: " << line << '\n';
+      return 1;
+    }
+    initial_state.add({std::stoul(m.str(1)), std::stoul(m.str(2))});
+  }
+
+  auto strength{initial_state.strength()};
+  std::vector<State> states;
+  states.push_back(initial_state);
+  while (!states.empty()) {
+    std::vector<State> next_states;
+    strength = 0;
+    auto inserter{std::back_inserter(next_states)};
+    for (auto const& state : states) {
+      strength = std::max(strength, state.strength());
+      state.next_states(inserter);
+    }
+    std::swap(states, next_states);
+  }
+
+  std::cout << "Max strength: " << strength << '\n';
+  return 0;
+}