From 3f7af92f6ddb727312530783f10d67cbd8525548 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Wed, 10 Dec 2025 15:12:37 +0100
Subject: aoc 2025, day 10, part 1

---
 2025/src/day10.cpp | 180 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 180 insertions(+)
 create mode 100644 2025/src/day10.cpp

(limited to '2025/src')

diff --git a/2025/src/day10.cpp b/2025/src/day10.cpp
new file mode 100644
index 0000000..f8e903d
--- /dev/null
+++ b/2025/src/day10.cpp
@@ -0,0 +1,180 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+class Machine {
+public:
+	Machine(unsigned long dest, const vector<unsigned long>& buttons)
+	    : dest_{ dest }
+	    , buttons_{ buttons }
+	{
+	}
+
+	void push(size_t button)
+	{
+		curr_ ^= buttons_.at(button);
+		++pushes_;
+	}
+
+	[[nodiscard]]
+	bool test() const
+	{
+		return curr_ == dest_;
+	}
+
+	void reset()
+	{
+		curr_   = 0;
+		pushes_ = 0;
+	}
+
+	[[nodiscard]]
+	unsigned long button_count() const
+	{
+		return buttons_.size();
+	}
+
+	[[nodiscard]]
+	unsigned long get_pushes() const
+	{
+		return pushes_;
+	}
+
+private:
+	unsigned long dest_;
+	unsigned long curr_{ 0 };
+	unsigned long pushes_{ 0 };
+
+	vector<unsigned long> buttons_;
+};
+
+vector<string>
+split(const string& str, const string& delims)
+{
+	vector<string> result;
+
+	size_t start = str.find_first_not_of(delims);
+	while ( start != string::npos ) {
+		size_t end = str.find_first_of(delims, start);
+
+		if ( end == string::npos ) {
+			// letzter Teil
+			result.push_back(str.substr(start));
+			break;
+		}
+
+		result.push_back(str.substr(start, end - start));
+
+		start = str.find_first_not_of(delims, end);
+	}
+
+	return result;
+}
+
+vector<unsigned long>
+split(const string& str)
+{
+	stringstream          strm{ str };
+	vector<unsigned long> values;
+
+	for ( string part; getline(strm, part, ','); ) {
+		values.emplace_back(stoul(part));
+	}
+
+	return values;
+}
+
+unsigned long
+from_pattern(string pattern)
+{
+	unsigned long value = 0;
+	ranges::reverse(pattern);
+	for ( const char chr: pattern ) {
+		value <<= 1UL;
+		value |= (chr == '#') ? 1U : 0U;
+	}
+	return value;
+}
+
+unsigned long
+from_button_string(const string& pattern)
+{
+	unsigned long value = 0;
+	for ( const auto pos: split(pattern) ) {
+		value |= (1UL << pos);
+	}
+	return value;
+}
+
+vector<Machine>
+read_file(const filesystem::path& filename)
+{
+	ifstream file{ filename };
+
+	vector<Machine> machines;
+
+	for ( string line; getline(file, line); ) {
+		const auto parts = split(line, "[] (){}");
+
+		const auto dest = from_pattern(parts[0]);
+
+		vector<unsigned long> buttons;
+		for ( size_t i = 1; i < parts.size() - 1; ++i ) {
+			buttons.emplace_back(from_button_string(parts[i]));
+		}
+
+		machines.emplace_back(dest, buttons);
+	}
+
+	return machines;
+}
+
+unsigned long
+simulate(Machine machine)
+{
+	auto min_so_far = numeric_limits<unsigned long>::max();
+
+	const auto button_count = machine.button_count();
+
+	for ( unsigned long i = 0; i != (1UL << button_count); ++i ) {
+		machine.reset();
+
+		for ( unsigned long button = 0; button != button_count; ++button ) {
+			if ( (i & (1UL << button)) != 0 ) {
+				machine.push(button);
+			}
+		}
+
+		if ( machine.test() ) {
+			min_so_far = min(min_so_far, machine.get_pushes());
+		}
+	}
+
+	return min_so_far;
+}
+
+void
+part1(const vector<Machine>& machines)
+{
+	unsigned long count = 0;
+	for ( const auto& machine: machines ) {
+		count += simulate(machine);
+	}
+	cout << "Part 1: " << count << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	auto machines = read_file("data/day10.txt");
+	part1(machines);
+}
-- 
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