Solutions for 2018 day 9

2018/puzzle-09-01.cc

@@ -0,0 +1,63 @@
+//
+// Created by Matthew Gretton-Dann on 01/12/2022.
+//
+
+#include <algorithm>
+#include <cstdlib>
+#include <iomanip>
+#include <iostream>
+#include <map>
+#include <regex>
+#include <utility>
+
+using UInt = std::uint64_t;
+using State = std::vector<UInt>;
+using Players = std::vector<UInt>;
+
+auto main() -> int
+{
+  std::string line;
+  std::regex const re{"(\\d+) players; last marble is worth (\\d+) points"};
+
+  // Read data
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Unable to read line.\n";
+    return EXIT_FAILURE;
+  }
+
+  std::smatch m;
+  if (!std::regex_match(line, m, re)) {
+    std::cerr << "Unable to interpret: " << line << "\n";
+    return EXIT_FAILURE;
+  }
+
+  UInt const player_count{std::stoull(m.str(1))};
+  UInt const last_marble{std::stoull(m.str(2))};
+
+  Players players(player_count, 0);
+
+  State game;
+  game.reserve(last_marble);
+  game.push_back(0);
+  UInt current_pos{0};
+
+  UInt player{0};
+  for (UInt marble{1}; marble <= last_marble; ++marble) {
+    if (marble % 23 == 0) {
+      players[player] += marble;
+      current_pos = (current_pos + game.size() - 7) % game.size();
+      players[player] += game.at(current_pos);
+      game.erase(game.begin() + static_cast<State::difference_type>(current_pos));
+      current_pos %= game.size();
+    }
+    else {
+      current_pos = (current_pos + 2) % game.size();
+      game.insert(game.begin() + static_cast<State::difference_type>(current_pos), marble);
+    }
+    player = (player + 1) % player_count;
+  }
+
+  auto max_elt{std::max_element(players.begin(), players.end())};
+  std::cout << "high score is: " << *max_elt << "\n";
+  return EXIT_SUCCESS;
+}

2018/puzzle-09-02.cc

@@ -0,0 +1,88 @@
+//
+// Created by Matthew Gretton-Dann on 01/12/2022.
+//
+
+#include <algorithm>
+#include <cstdlib>
+#include <iomanip>
+#include <iostream>
+#include <list>
+#include <map>
+#include <regex>
+#include <utility>
+
+using UInt = std::uint64_t;
+using Int = std::int64_t;
+using State = std::list<UInt>;
+using Players = std::vector<UInt>;
+
+template<typename iterator>
+auto move(iterator begin, iterator end, iterator current, Int count)
+{
+  while (count > 0) {
+    if (current == end) {
+      current = begin;
+    }
+    ++current;
+    --count;
+  }
+  while (count < 0) {
+    if (current == begin) {
+      current = end;
+    }
+    --current;
+    ++count;
+  }
+  if (current == end) {
+    current = begin;
+  }
+  return current;
+}
+
+auto main() -> int
+{
+  std::string line;
+  std::regex const re{"(\\d+) players; last marble is worth (\\d+) points"};
+
+  // Read data
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Unable to read line.\n";
+    return EXIT_FAILURE;
+  }
+
+  std::smatch m;
+  if (!std::regex_match(line, m, re)) {
+    std::cerr << "Unable to interpret: " << line << "\n";
+    return EXIT_FAILURE;
+  }
+
+  UInt const player_count{std::stoull(m.str(1))};
+  UInt const last_marble{std::stoull(m.str(2)) * 100};
+
+  Players players(player_count, 0);
+
+  State game;
+  game.push_back(0);
+  auto current_pos{game.begin()};
+
+  UInt player{0};
+  for (UInt marble{1}; marble <= last_marble; ++marble) {
+    if (marble % 23 == 0) {
+      current_pos = move(game.begin(), game.end(), current_pos, -7);
+      players[player] += marble + *current_pos;
+      current_pos = game.erase(current_pos);
+      if (current_pos == game.end()) {
+        current_pos = game.begin();
+      }
+    }
+    else {
+      current_pos = move(game.begin(), game.end(), current_pos, 2);
+      current_pos = game.insert(current_pos, marble);
+    }
+    player = (player + 1) % player_count;
+  }
+
+  auto max_elt{std::max_element(players.begin(), players.end())};
+  std::cout << "high score is: " << *max_elt << "\n";
+  return EXIT_SUCCESS;
+}