Add 2021 day 11 puzzles

2021/puzzle-11-01.cc

@@ -0,0 +1,83 @@
+//
+// Created by Matthew Gretton-Dann on 11/12/2021.
+//
+
+#include <iostream>
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+using Coord = std::pair<int, int>;
+
+struct State
+{
+  State(std::vector<std::string> const& initial)
+  {
+    for (int y = 0; y < initial.size(); ++y) {
+      for (int x = 0; x < initial[y].size(); ++x) {
+        octopi_.insert({{x, y}, initial[y][x] - '0'});
+      }
+    }
+  }
+
+  unsigned sparkle()
+  {
+    std::set<Coord> visited;
+    // Start by incrementing every octopus by one.
+    for (auto& o : octopi_) {
+      (o.second)++;
+    }
+
+    auto just_visited{0};
+    do {
+      just_visited = visited.size();
+      for (auto const& o : octopi_) {
+        if (o.second > 9 && !visited.contains(o.first)) {
+          visited.insert({o.first});
+          for (int x = o.first.first - 1; x < o.first.first + 2; ++x) {
+            for (int y = o.first.second - 1; y < o.first.second + 2; ++y) {
+              auto it{octopi_.find({x, y})};
+              if (it != octopi_.end()) {
+                ++(it->second);
+              }
+            }
+          }
+        }
+      }
+    } while (just_visited != visited.size());
+
+    // And reset the energy levels
+    for (auto& o : octopi_) {
+      if (o.second > 9) {
+        o.second = 0;
+      }
+    }
+
+    return visited.size();
+  }
+
+private:
+  std::map<Coord, unsigned> octopi_;
+};
+
+auto main() -> int
+{
+  std::string line;
+  std::vector<std::string> lines;
+
+  while (std::getline(std::cin, line)) {
+    lines.push_back(line);
+  }
+
+  State octopi(lines);
+
+  constexpr unsigned max_steps{100};
+  unsigned count{0};
+  for (unsigned i = 0; i < max_steps; ++i) {
+    count += octopi.sparkle();
+  }
+
+  std::cout << "After " << max_steps << " we have sparkled " << count << " times.\n";
+  return 0;
+}

2021/puzzle-11-02.cc

@@ -0,0 +1,84 @@
+//
+// Created by Matthew Gretton-Dann on 11/12/2021.
+//
+
+#include <iostream>
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+using Coord = std::pair<int, int>;
+
+struct State
+{
+  State(std::vector<std::string> const& initial)
+  {
+    for (int y = 0; y < initial.size(); ++y) {
+      for (int x = 0; x < initial[y].size(); ++x) {
+        octopi_.insert({{x, y}, initial[y][x] - '0'});
+      }
+    }
+  }
+
+  unsigned sparkle()
+  {
+    std::set<Coord> visited;
+    // Start by incrementing every octopus by one.
+    for (auto& o : octopi_) {
+      (o.second)++;
+    }
+
+    auto just_visited{0};
+    do {
+      just_visited = visited.size();
+      for (auto const& o : octopi_) {
+        if (o.second > 9 && !visited.contains(o.first)) {
+          visited.insert({o.first});
+          for (int x = o.first.first - 1; x < o.first.first + 2; ++x) {
+            for (int y = o.first.second - 1; y < o.first.second + 2; ++y) {
+              auto it{octopi_.find({x, y})};
+              if (it != octopi_.end()) {
+                ++(it->second);
+              }
+            }
+          }
+        }
+      }
+    } while (just_visited != visited.size());
+
+    // And reset the energy levels
+    for (auto& o : octopi_) {
+      if (o.second > 9) {
+        o.second = 0;
+      }
+    }
+
+    return visited.size();
+  }
+
+private:
+  std::map<Coord, unsigned> octopi_;
+};
+
+auto main() -> int
+{
+  std::string line;
+  std::vector<std::string> lines;
+
+  unsigned grid_size{0};
+  while (std::getline(std::cin, line)) {
+    grid_size += line.size();
+    lines.push_back(line);
+  }
+
+  State octopi(lines);
+  unsigned step{0};
+
+  do {
+    ++step;
+  } while (octopi.sparkle() != grid_size);
+
+  std::cout << "Synchronization after " << step << " steps.\n";
+  return 0;
+}