From 756f22d58bb198b8f34589c112e1003614ccdcd6 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Sun, 2 Nov 2025 21:41:58 +0100
Subject: aoc 2017, days 1-20

---
 2017/src/day08.cpp | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 2017/src/day08.cpp

(limited to '2017/src/day08.cpp')

diff --git a/2017/src/day08.cpp b/2017/src/day08.cpp
new file mode 100644
index 0000000..64c1ea0
--- /dev/null
+++ b/2017/src/day08.cpp
@@ -0,0 +1,118 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <sstream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+vector<string>
+split(const string& line, char sep = ' ')
+{
+	stringstream   strm{ line };
+	vector<string> parts;
+
+	for ( string part; getline(strm, part, sep); ) {
+		parts.emplace_back(part);
+	}
+
+	return parts;
+}
+
+vector<vector<string>>
+read_file(const filesystem::path& filename)
+{
+	ifstream               file{ filename };
+	vector<vector<string>> data;
+
+	for ( string line; getline(file, line); ) {
+		auto parts = split(line);
+		data.emplace_back(parts);
+	}
+
+	return data;
+}
+
+void
+compute(const vector<vector<string>>& data, map<string, int>& memory, int& max_value)
+{
+	auto match = [](int lhs, string_view rel, int rhs) {
+		if ( rel == "==" ) {
+			return lhs == rhs;
+		}
+		else if ( rel == "!=" ) {
+			return lhs != rhs;
+		}
+		else if ( rel == "<" ) {
+			return lhs < rhs;
+		}
+		else if ( rel == "<=" ) {
+			return lhs <= rhs;
+		}
+		else if ( rel == ">" ) {
+			return lhs > rhs;
+		}
+		else if ( rel == ">=" ) {
+			return lhs >= rhs;
+		}
+
+		throw runtime_error("unknown relation operator: "s + string(rel));
+	};
+
+	auto execute = [&](const string& reg, string_view opcode, int value) {
+		if ( opcode == "inc" ) {
+			memory[reg] += value;
+		}
+		else if ( opcode == "dec" ) {
+			memory[reg] -= value;
+		}
+		else {
+			throw runtime_error("unknown opcode: "s + string(opcode));
+		}
+	};
+
+	for ( const auto& instr: data ) {
+		const auto& reg    = instr.at(0);
+		const auto& opcode = instr.at(1);
+		const auto  value  = stoi(instr.at(2));
+		const auto  lhs    = memory[instr.at(4)];
+		const auto& rel    = instr.at(5);
+		const auto  rhs    = stoi(instr.at(6));
+
+		if ( match(lhs, rel, rhs) ) {
+			execute(reg, opcode, value);
+			max_value = max(max_value, memory[reg]);
+		}
+	}
+}
+
+void
+solve(const vector<vector<string>>& data)
+{
+	map<string, int> memory;
+	auto             max_value = numeric_limits<int>::min();
+
+	compute(data, memory, max_value);
+
+	auto itr = ranges::max_element(memory, [](const auto& lhs, const auto& rhs) { return lhs.second < rhs.second; });
+	cout << "Part1: " << itr->second << '\n';
+	cout << "Part2: " << max_value << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	auto data = read_file("data/day08.txt");
+	try {
+		solve(data);
+	}
+	catch ( exception& e ) {
+		cerr << "Fehler: " << e.what() << '\n';
+	}
+}
-- 
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