1024

3 files changed, 49 insertions, 9 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4782b07..f0fbd5e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.8)
 project(advent-of-code LANGUAGES CXX)
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -O3 -Wall -Wextra -pedantic -Wno-unused-parameter")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -O3 -Wall -Wextra -pedantic -Wno-unused-parameter")
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_EXTENSIONS Off)
 
diff --git a/src/2015/day6/aoc.h b/src/2015/day6/aoc.h
index c178277..b68ef18 100644
--- a/src/2015/day6/aoc.h
+++ b/src/2015/day6/aoc.h
@@ -4,36 +4,70 @@
 
 namespace aoc2015 {
 
+template <size_t N>
 struct grid {
-  uint8_t* pool;
+  static_assert(N > 0 && ((N & (N - 1)) == 0), "N must be power of 2");
+  constexpr static size_t size = N * N / 64;
+
+  uint64_t pool[size] = {0};
 
   struct unit {
     int x;
     int y;
   };
 
-  grid(int x, int y) {
-    pool = (uint8_t*)malloc(x * y);
-    memset(pool, 0x0, x * y);
+  void set(int x, int y) {
+    uint64_t p = x * N + y;
+    uint64_t r = p >> 6;
+    uint64_t c = p & 63;
+    uint64_t& byte = pool[r];
+    uint64_t mask = 1 << c;
+    byte |= mask;
+  }
+
+  void reset(int x, int y) {
+    uint64_t p = x * N + y;
+    uint64_t r = p >> 6;
+    uint64_t c = p & 63;
+    uint64_t& byte = pool[r];
+    uint64_t mask = ~(1 << c);
+    byte &= mask;
+  }
+
+  void toggle(int x, int y) {
+    uint64_t p = x * N + y;
+    uint64_t r = p >> 6;
+    uint64_t c = p & 63;
+    uint64_t& byte = pool[r];
+    uint64_t mask = 1 << c;
+    byte ^= mask;
+  }
+
+  int count() const noexcept {
+    int total = 0;
+    for (uint64_t i : pool) {
+       total += __builtin_popcountll(i);
+    }
+    return total;
   }
 
   template <typename F, typename... Args>
   void traverse(unit u1, unit u2, F&& f, Args&&... args) {
     for (int i = u1.x; i <= u2.x; i++) {
       for (int j = u1.y; j <= u2.y; j++) {
-        f(pool[i * j], std::forward<Args>(args)...);
+        f(i, j, std::forward<Args>(args)...);
       }
     }
   }
 
   void turn_on(unit u1, unit u2) {
-    traverse(u1, u2, [](uint8_t& u) { u = 1; });
+    traverse(u1, u2, [this](int i, int j) { set(i, j); });
   }
   void turn_off(unit u1, unit u2) {
-    traverse(u1, u2, [](uint8_t& u) { u = 0; });
+    traverse(u1, u2, [this](int i, int j) { reset(i, j); });
   }
   void toggle(unit u1, unit u2) {
-    traverse(u1, u2, [](uint8_t& u) { u = !u; });
+    traverse(u1, u2, [this](int i, int j) { toggle(i, j); });
   }
 };
 
diff --git a/test/test_2015.cpp b/test/test_2015.cpp
index 5a55d13..a6bb135 100644
--- a/test/test_2015.cpp
+++ b/test/test_2015.cpp
@@ -72,3 +72,9 @@ TEST_CASE("Doesn't He Have Intern-Elves For This?", "[day5]") {
   REQUIRE(p.first == 255);
   REQUIRE(p.second == 55);
 }
+
+TEST_CASE("Probably a Fire Hazard", "[day6]") {
+  aoc2015::grid<1024> grid;
+  grid.turn_on({0,0}, {0,999});
+  REQUIRE(grid.count() == 1000);
+}