1 files changed, 114 insertions, 0 deletions

diff --git a/2015/src/day06.cpp b/2015/src/day06.cpp
new file mode 100644
index 0000000..b7f15b5
--- /dev/null
+++ b/2015/src/day06.cpp
@@ -0,0 +1,114 @@
+#include <algorithm>
+#include <cstdio>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <string>
+#include <tuple>
+#include <vector>
+
+using namespace std;
+
+enum Operation {
+        On,
+        Off,
+        Toggle
+};
+
+using instruction = tuple<Operation, int, int, int, int>;
+
+auto
+read_file(string_view filename)
+{
+        fstream             input{ filename };
+        vector<instruction> instructions;
+
+        for ( string line; getline(input, line); ) {
+                int x0, y0, x1, y1; // NOLINT
+
+                if ( sscanf(line.c_str(), "turn on %d,%d through %d,%d", &x0, &y0, &x1, &y1) == 4 ) { // NOLINT
+                        instructions.emplace_back(Operation::On, x0, y0, x1, y1);
+                }
+                else if ( sscanf(line.c_str(), "toggle %d,%d through %d,%d", &x0, &y0, &x1, &y1) == 4 ) { // NOLINT
+                        instructions.emplace_back(Operation::Toggle, x0, y0, x1, y1);
+                }
+                else if ( sscanf(line.c_str(), "turn off %d,%d through %d,%d", &x0, &y0, &x1, &y1) == 4 ) { // NOLINT
+                        instructions.emplace_back(Operation::Off, x0, y0, x1, y1);
+                }
+        }
+
+        return instructions;
+}
+
+// clang-format off
+static void turn_on(int& value) { value = 1; }
+static void turn_off(int& value) { value = 0; }
+static void toggle(int& value) { value ^= 1; }
+// clang-format on
+
+void
+part1(const vector<instruction>& instructions)
+{
+        map<Operation, function<void(int&)>> ops = {
+                { Operation::On, turn_on },
+                { Operation::Toggle, toggle },
+                { Operation::Off, turn_off }
+        };
+
+        map<tuple<int, int>, int> lights;
+
+        for ( const auto& [operation, x0, y0, x1, y1]: instructions ) {
+                for ( int x = x0; x <= x1; ++x ) {
+                        for ( int y = y0; y <= y1; ++y ) {
+                                ops[operation](lights[{ x, y }]);
+                        }
+                }
+        }
+
+        auto sum = count_if(begin(lights), end(lights), [](const auto& light) {
+                return light.second == 1;
+        });
+
+        cout << sum << endl;
+}
+
+// clang-format off
+static void increase(int& value) { ++value; }
+static void decrease(int& value) { if (value > 0) { --value; } }
+static void increase_by_2(int& value) { value += 2; }
+// clang-format on
+
+void
+part2(const vector<instruction>& instructions)
+{
+        map<Operation, function<void(int&)>> ops = {
+                { Operation::On, increase },
+                { Operation::Toggle, increase_by_2 },
+                { Operation::Off, decrease }
+        };
+
+        map<tuple<int, int>, int> lights;
+
+        for ( const auto& [operation, x0, y0, x1, y1]: instructions ) {
+                for ( int x = x0; x <= x1; ++x ) {
+                        for ( int y = y0; y <= y1; ++y ) {
+                                ops[operation](lights[{ x, y }]);
+                        }
+                }
+        }
+
+        auto sum = accumulate(begin(lights), end(lights), 0, [](int value, const auto& light) {
+                return value + light.second;
+        });
+
+        cout << sum << endl;
+}
+
+int
+main()
+{
+        auto instructions = read_file("data/day06.txt");
+        part1(instructions);
+        part2(instructions);
+}