From e67bd318726418f37d1541939ac3e97667995d8d Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Mon, 18 Dec 2023 19:12:58 +0100
Subject: Lösungen für Tag 18
MIME-Version: 1.0
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---
 src/day18.cpp | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 src/day18.cpp

(limited to 'src')

diff --git a/src/day18.cpp b/src/day18.cpp
new file mode 100644
index 0000000..3037739
--- /dev/null
+++ b/src/day18.cpp
@@ -0,0 +1,115 @@
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <sstream>
+#include <string>
+#include <vector>
+using namespace std;
+
+using puzzle_t = vector<pair<long, long>>;
+
+puzzle_t
+read_file_part1(string_view filename, long& border_steps)
+{
+	static map<char, pair<int, int>> movement = {
+		{ 'U', { 0, -1 } }, // up
+		{ 'D', { 0, 1 } },  // down
+		{ 'L', { -1, 0 } }, // left
+		{ 'R', { 1, 0 } },  // right
+	};
+
+	border_steps = 0;
+
+	fstream  input{ filename };
+	puzzle_t data;
+
+	data.emplace_back(0, 0);
+
+	for ( string line; getline(input, line); ) {
+		char         dir{};
+		long         steps{};
+		stringstream sstrm{ line };
+
+		if ( sstrm >> dir >> steps ) {
+			data.emplace_back(get<0>(data.back()) + get<0>(movement[dir]) * steps,
+			                  get<1>(data.back()) + get<1>(movement[dir]) * steps);
+
+			border_steps += steps;
+		}
+	}
+
+	return data;
+}
+
+puzzle_t
+read_file_part2(string_view filename, long& border_steps)
+{
+	static map<char, pair<int, int>> movement = {
+		{ '0', { 1, 0 } },  // right
+		{ '1', { 0, 1 } },  // down
+		{ '2', { -1, 0 } }, // left
+		{ '3', { 0, -1 } }, // up
+	};
+
+	border_steps = 0;
+
+	fstream  input{ filename };
+	puzzle_t data;
+
+	data.emplace_back(0, 0);
+
+	for ( string line; getline(input, line); ) {
+		char         dir{};
+		long         steps{};
+		string       hexcode;
+		stringstream sstrm{ line };
+
+		if ( sstrm >> dir >> steps >> hexcode ) {
+			steps = stol(hexcode.substr(2, 5), nullptr, 16);
+			dir   = hexcode[7];
+
+			data.emplace_back(get<0>(data.back()) + get<0>(movement[dir]) * steps,
+			                  get<1>(data.back()) + get<1>(movement[dir]) * steps);
+
+			border_steps += steps;
+		}
+	}
+
+	return data;
+}
+
+long
+shoelace(const puzzle_t& puzzle, const long border_steps)
+{
+	long area = 0;
+	for ( size_t i = 1; i < puzzle.size(); ++i ) {
+		const auto [x1, y1] = puzzle[i - 1];
+		const auto [x2, y2] = puzzle[i];
+
+		area += (x1 * y2 - y1 * x2);
+	}
+	return (border_steps + area) / 2 + 1;
+}
+
+void
+part1()
+{
+	long border_steps = 0;
+	auto puzzle       = read_file_part1("data/day18.txt", border_steps);
+	cout << shoelace(puzzle, border_steps) << endl;
+}
+
+void
+part2()
+{
+	long border_steps = 0;
+	auto puzzle       = read_file_part2("data/day18.txt", border_steps);
+	cout << shoelace(puzzle, border_steps) << endl;
+}
+
+int
+main()
+{
+	part1();
+	part2();
+}
-- 
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