Initial commit

2020/puzzle-17-02.cc

@@ -0,0 +1,91 @@
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <iostream>
+#include <list>
+#include <map>
+#include <regex>
+#include <set>
+#include <string>
+#include <tuple>
+
+struct ConwayCubeState {
+  using Point = std::tuple<int, int, int, int>;
+  using PointSet = std::set<Point>;
+  using NeighbourMap = std::map<Point, unsigned>;
+
+  ConwayCubeState() : next_row_(0) {}
+  void add_row(std::string const &s) {
+    for (int x = 0; x < s.size(); ++x) {
+      if (s[x] == '#') {
+        set_point(x, next_row_, 0, 0);
+      }
+    }
+    ++next_row_;
+  }
+
+  ConwayCubeState next_state() const {
+    ConwayCubeState next;
+    for (auto const &n : neighbours_) {
+      bool active = points_.find(n.first) != points_.end();
+      if (active && (n.second == 2 || n.second == 3)) {
+        next.set_point(n.first);
+      } else if (!active && n.second == 3) {
+        next.set_point(n.first);
+      }
+    }
+
+    return next;
+  }
+
+  auto active() const { return points_.size(); }
+
+private:
+  void set_point(Point const &pt) {
+    set_point(std::get<0>(pt), std::get<1>(pt), std::get<2>(pt),
+              std::get<3>(pt));
+  }
+
+  void set_point(int pw, int px, int py, int pz) {
+    points_.insert({pw, px, py, pz});
+
+    for (int w = pw - 1; w < pw + 2; ++w) {
+      for (int x = px - 1; x < px + 2; ++x) {
+        for (int y = py - 1; y < py + 2; ++y) {
+          for (int z = pz - 1; z < pz + 2; ++z) {
+            if (w == pw && x == px && y == py && z == pz) {
+              continue;
+            }
+            auto [it, success] = neighbours_.insert({{w, x, y, z}, 1});
+            if (!success) {
+              assert(it != neighbours_.end());
+              it->second += 1;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  int next_row_;
+  PointSet points_;
+  NeighbourMap neighbours_;
+};
+
+int main(void) {
+  std::string line;
+  ConwayCubeState state;
+  while (std::getline(std::cin, line)) {
+    state.add_row(line);
+    std::cout << line << "\n";
+  }
+
+  std::cout << "Initial active count = " << state.active() << "\n";
+
+  for (unsigned i = 0; i < 6; ++i) {
+    state = state.next_state();
+    std::cout << i + 1 << ": active count = " << state.active() << "\n";
+  }
+
+  return 0;
+}