From da5d346f8703f3d6676f940968d2569a1d14b4b5 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Tue, 14 Jan 2025 23:17:35 +0100
Subject: aoc 2016, day 8

---
 2016/src/day08.cpp | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 2016/src/day08.cpp

(limited to '2016/src')

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);
+}
-- 
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