1 files changed, 101 insertions, 0 deletions

diff --git a/2016/src/day08.cpp b/2016/src/day08.cpp
new file mode 100644
index 0000000..ab3fc88
--- /dev/null
+++ b/2016/src/day08.cpp
@@ -0,0 +1,101 @@
+#include <algorithm>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+vector<tuple<char, size_t, size_t>>
+read_file(string_view filename)
+{
+        fstream input{ filename };
+
+        vector<tuple<char, size_t, size_t>> instr;
+
+        for ( string line; getline(input, line); ) {
+                size_t value_a = 0;
+                size_t value_b = 0;
+
+                if ( sscanf(line.c_str(), "rect %zu x %zu", &value_a, &value_b) == 2 ) {
+                        instr.emplace_back('r', value_a, value_b);
+                }
+                else if ( sscanf(line.c_str(), "rotate column x=%zu by %zu", &value_a, &value_b) == 2 ) {
+                        instr.emplace_back('x', value_a, value_b);
+                }
+                else if ( sscanf(line.c_str(), "rotate row y=%zu by %zu", &value_a, &value_b) == 2 ) {
+                        instr.emplace_back('y', value_a, value_b);
+                }
+        }
+
+        return instr;
+}
+
+void
+solve(const vector<tuple<char, size_t, size_t>>& instr)
+{
+        static const size_t width  = 50;
+        static const size_t height = 6;
+
+        map<tuple<size_t, size_t>, char> disp;
+
+        auto reverse_y = [&](const size_t y, size_t lhs, size_t rhs) {
+                while ( lhs < rhs ) {
+                        swap(disp[{ lhs++, y }], disp[{ --rhs, y }]);
+                }
+        };
+
+        auto rotate_y = [&](const size_t y, const size_t num) {
+                reverse_y(y, 0, width);
+                reverse_y(y, 0, num);
+                reverse_y(y, num, width);
+        };
+
+        auto reverse_x = [&](const size_t x, size_t lhs, size_t rhs) {
+                while ( lhs < rhs ) {
+                        swap(disp[{ x, lhs++ }], disp[{ x, --rhs }]);
+                }
+        };
+
+        auto rotate_x = [&](const size_t x, const size_t num) {
+                reverse_x(x, 0, height);
+                reverse_x(x, 0, num);
+                reverse_x(x, num, height);
+        };
+
+        for ( const auto& [chr, val_a, val_b]: instr ) {
+                if ( chr == 'r' ) {
+                        for ( size_t x = 0; x != val_a; ++x ) {
+                                for ( size_t y = 0; y != val_b; ++y ) {
+                                        disp[{ x, y }] = '#';
+                                }
+                        }
+                }
+                else if ( chr == 'x' ) {
+                        rotate_x(val_a, val_b);
+                }
+                else if ( chr == 'y' ) {
+                        rotate_y(val_a, val_b);
+                }
+        }
+
+        // part1
+        cout << count_if(disp.begin(), disp.end(), [](auto pos) { return pos.second == '#'; }) << endl;
+
+        // part2
+        for ( size_t y = 0; y != height; ++y ) {
+                for ( size_t x = 0; x != width; ++x ) {
+                        cout << ((disp[{ x, y }] == '#') ? '#' : ' ');
+                }
+                cout << endl;
+        }
+        cout << endl;
+}
+
+int
+main()
+{
+        auto instr = read_file("data/day08.txt");
+        solve(instr);
+}